JP2010023307A - Screen printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screen printing method, in which the positioning between a screen mask and a material to be printed is executed enough accurately in a screen printing so as to enough accurately print an object printing pattern on the material to be printed. <P>SOLUTION: In the screen printing method, in which a printing pattern is printed through opening apertures on the material to be printed after the positioning between the screen mask having the opening apertures corresponding to the printing pattern and the material to be printed has been executed, the positioning is executed by relatively moving the material to be printed and the screen mask so as to remove the discrepancy between the positions of shadows and the positions of the positioning references on the material to be printed side under the state that positioning references are provided on the screen mask and on the material to be printed so as to irradiate light from just above the positioning references on the screen mask side in order to project the shadows of the positioning references on the screen mask side on the material to be printed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a screen printing method capable of accurately printing a print pattern at a desired position on a printing material in screen printing for forming a target printing pattern on the printing material.

  For example, in one of the manufacturing processes of image display devices such as flat panel displays and electronic parts such as ceramic parts, printed boards and solar cells, electrodes and light emission are formed in recesses such as grooves and holes formed on various boards. There is a step of forming a layer. The electrode and the light emitting layer are formed by filling a concave portion formed on the substrate with a conductive or luminescent paste-like printing material, and these materials are sufficiently filled in the concave portion and around the concave portion. It is required that these materials do not protrude on the substrate surface.

  As a method of filling these materials into the concave portions of the substrate, photolithography, ink jet printing, and the like have been used. However, these methods can accurately fill the recesses with a conductive or luminescent printing material with a high filling rate, but on the other hand, there is a problem that the cost required for the production becomes large.

Therefore, for the purpose of reducing the cost required for production, an electrode or a light emitting layer is formed by filling the above-mentioned material into a concave portion formed on a substrate using screen printing.
As a method of filling a concave portion formed on the substrate by screen printing with a conductive or luminescent printing material, for example, as shown in FIG. 2, first, on the substrate that is the substrate 1 on which the concave portion 12 is formed, The screen mask 2 provided with the opening window 9 is installed at a position corresponding to the recess 12.

Then, the printing material 11 is supplied onto the screen mask 2, and a scraper (not shown) is translated on the screen mask 2 to fill the opening window 9 with the printing material 11. Thereafter, the squeegee 10 is brought into contact with the screen mask 2, and the squeegee 10 is moved in parallel while pressing the screen mask 2 against the substrate with the squeegee 10, so that the printing material 11 filled in the opening window 9 is placed in the recess 12 on the substrate. Extrude and fill the recess 12 with the printing material 11.
Here, in order to perform printing with high accuracy, it is important that the positions of the opening window 9 and the recess 12 of the screen mask 2 coincide. That is, in screen printing, it is necessary to position the substrate and the screen mask.

  By repeating a series of operations as described above, a substrate in which the recess 12 is filled with the conductive or luminescent printing material 11 is produced. By using the screen printing method, the number of processes and the processing speed can be increased as compared with photolithography and inkjet printing, and the cost required for production can be reduced.

  In addition, when a solar cell electrode is formed by such a screen printing method, for example, a conductive paste material is used as a paste-like printing material. The height is limited to half of the line width of the electrode formed in (1), and it is difficult to form an electrode with a thin and thick line width, that is, a high aspect ratio by one screen printing. .

Therefore, in order to obtain an electrode that requires a high aspect ratio, such as a finger electrode of a solar cell, screen printing is repeated a plurality of times, and a conductive paste is overlaid on the lower electrode wire and printed. An electrode having a structure is formed.
However, when an electrode having a multi-layer structure is formed in this way, if there is a shift between the pattern of the lower electrode line and the position of the opening window of the screen mask, the electrode pattern that should be stacked vertically is gradually little by little. There is a problem that a shift such as tilting occurs between the layers, a stable characteristic cannot be obtained, and a shadow loss of the electrode occurs.

Thus, in screen printing, it is necessary to accurately position the substrate to be printed and the screen mask. Conventionally, for example, the following positioning method has been used.
FIG. 3 is an explanatory schematic diagram showing an example of a conventional positioning method during screen printing.
The substrate 1 is placed and fixed on the printing stage 8. Then, while checking the position of the substrate 1 with the camera 7, the substrate 1 is positioned by finely moving the printing stage 8 by mechanical edge alignment or centering.
Thereafter, the printing stage 8 moves by a predetermined amount just below the screen mask 2, and then a printing pattern is screen-printed on the substrate.

  However, even if the printing substrate 1 is accurately positioned directly under the camera 7, when the printing stage 8 moves a predetermined amount directly under the screen mask 2, for example, by frictional heat of a ball screw used as a moving means, etc. Distortion occurs at the connection between the printing stage 8 and the ball screw. Due to this distortion, an error occurs in the moving distance of the printing stage 8, and a deviation occurs between the printing position of the printing pattern on the printing material and the opening window of the screen mask. For this reason, there has been a problem that the position of the printed print pattern is deviated from the position to be originally printed.

To solve this problem, a method is disclosed in which when the moving printing stage contacts the stopper, the driving force of the motor is absorbed by a compression spring to accurately position the printing stage and perform screen printing (see Patent Document 1). ).
However, in this method, there is a problem that the compression spring and the sensor must be adjusted frequently, and when the entire printing press is distorted by frictional heat, the displacement cannot be absorbed.
Patent Publication No. 7-136889

  The present invention has been made in view of the above-described problems. In screen printing, the screen mask and the substrate can be accurately positioned, and the target print pattern can be accurately printed on the substrate. An object is to provide a printing method.

  In order to achieve the above object, according to the present invention, after positioning a screen mask having an opening window corresponding to a printing pattern and the printing material, the printing pattern is printed on the printing material through the opening window. In the screen printing method, the positioning is performed by providing a positioning reference for the screen mask and the substrate to be printed, and irradiating light from directly above the positioning reference on the screen mask side to position the positioning reference for the screen mask on the substrate. Screen printing, which is performed by relatively moving the substrate and the screen mask so as to eliminate the deviation between the position of the shadow and the positioning reference position on the substrate side A method is provided (claim 1).

  As described above, the positioning reference is provided to the screen mask and the substrate, and light is irradiated from directly above the positioning reference on the screen mask side so that the positioning reference on the screen mask side is applied to the substrate. By projecting a shadow and relatively moving the substrate and the screen mask so as to eliminate the deviation between the position of the shadow and the positioning reference position on the substrate, Positioning with the substrate can be performed with high accuracy, and a target print pattern can be printed with high accuracy on the substrate.

  At this time, when positioning the printing substrate and the screen mask, the shadow and the image of the positioning reference on the printing substrate side are taken into an image processing means, and the image is image-processed to calculate the amount of deviation, The printing substrate and the screen mask can be relatively moved by the calculated amount of displacement for positioning.

  As described above, when positioning the printing substrate and the screen mask, the shadow and the positioning reference image on the printing substrate side are taken into an image processing unit, and the image is processed to calculate the amount of deviation. By positioning the substrate and the screen mask by relatively moving the calculated displacement amount, the screen mask and the substrate can be positioned more accurately during printing, and the process is automated. can do.

At this time, the substrate may be a solar cell electrode.
The screen printing method of the present invention is particularly useful in the screen printing of solar cell electrodes that require high accuracy and low cost because the target printing pattern can be accurately printed on the substrate.

At this time, an alignment mark can be used as a positioning reference for the screen mask and the substrate.
Thus, if the alignment mark is used as the positioning reference for the screen mask and the substrate, the positioning reference can be set specifically, and positioning can be performed easily and accurately.

  Further, at this time, the printed material is an electrode of a solar cell on which an electrode pattern is printed on the first layer, the electrode pattern on the first layer is used as a positioning reference on the printed material side, and the screen mask As a positioning reference on the side, an aperture window corresponding to the electrode pattern of the solar cell to be printed is used, and an electrode pattern of at least one layer is printed on the electrode pattern of the first layer. (Claim 5).

  As described above, the printed material is an electrode of a solar cell on which an electrode pattern is printed on the first layer, and the first layer electrode pattern is used as a positioning reference on the printed material side, and the screen mask is used. As a positioning reference on the side, an aperture window corresponding to the electrode pattern of the solar cell to be printed is used, and an electrode pattern of at least one layer is printed on the electrode pattern of the first layer. By doing so, the positioning reference can be set specifically even without the alignment mark, and the electrode pattern can be printed with high accuracy. That is, it is possible to screen print an electrode having a multilayer structure with reduced shadow loss.

  In the present invention, in the screen printing, positioning is performed by providing a positioning reference for the screen mask and the printed material, and irradiating light from directly above the positioning reference on the screen mask side, thereby positioning the screen mask side on the printed material. Is performed by relatively moving the substrate and the screen mask so as to eliminate the shift between the position of the shadow and the position of the positioning reference on the substrate side. And the target print pattern can be printed on the substrate with high accuracy.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
Conventionally, when forming an electronic component of a printed board, an electrode of a solar cell, or the like, a method of screen printing a conductive paste-like printing material on the board has been used. However, when screen printing a target print pattern on a substrate, there is a problem that the target print pattern cannot be accurately printed on the substrate at a desired position due to the displacement between the substrate and the screen mask. It was.

  Therefore, the present inventor has intensively studied to solve such problems. As a result, in order to accurately position the substrate to be printed and the screen mask, a positioning reference is provided for the screen mask and the substrate, and the shadow of the positioning reference on the screen mask side is projected onto the substrate by light irradiation. The present invention has been completed by conceiving that positioning can be performed with high precision by correcting the position by comparing the position of the shadow with the positioning reference position on the substrate side.

The screen printing method of the present invention will be described by taking as an example a step of filling a groove-like recess formed on a substrate with a conductive paste to form an electrode in a solar cell manufacturing process.
First, a substrate to be printed on which a printing pattern is printed and a screen mask having an opening window corresponding to the printing pattern are prepared. As the substrate, for example, a silicon single crystal wafer can be used. This silicon single crystal wafer is provided with a groove-like recess (electrode pattern) formed in advance by grinding.

The screen mask is provided with an opening window at a position corresponding to a printing pattern, that is, a groove-like recess on the wafer surface. Then, a positioning reference that is used as a reference when positioning both of the printing material and the screen mask is provided.
At this time, the positioning reference of the substrate and the screen mask can be used as the alignment mark. If an alignment mark is provided as a positioning reference, positioning can be performed easily and accurately.

  Here, a plurality of alignment marks can be provided. If at least two or more are provided, the positioning accuracy can be further improved. In addition, the alignment mark may be provided at any position on the substrate to be printed and the screen mask, and the alignment mark on the substrate to be printed and the screen mask may be configured to correspond to each other. Positioning errors due to distortion of the screen mask can be reduced by providing the central portion with less distortion.

Next, as shown in FIG. 1, the printing stage 8 is lowered, and the wafer that is the substrate 1 is placed and fixed on the printing stage 8. Then, a screen mask 2 is installed above the wafer 1.
Thereafter, light is irradiated by the light 5 from directly above the alignment mark 4 on the screen mask 2 side. In this way, by irradiating light from directly above the alignment mark 4, the shadow 6 of the alignment mark 4 on the screen mask 2 side is projected onto the wafer 1.

  Positioning with very little error is performed by relatively moving the wafer 1 (printing stage 8) and the screen mask 2 so as to eliminate the deviation between the position of the shadow 6 and the position of the alignment mark 3 on the wafer 1 side. be able to.

At this time, the image of the shadow 6 and the alignment mark 3 on the wafer 1 which is the substrate 1 is taken into the image processing means by using the camera 7, and the image is processed to obtain the shadow 6 and the alignment mark 3 on the wafer 1 side. The amount of positional deviation can be calculated, and the wafer 1 and the screen mask 2 can be positioned relative to each other by moving the calculated amount of deviation.
Thus, by calculating the amount of displacement between the shadow 6 and the image of the alignment mark 3 on the wafer side that is the substrate 1 captured by the camera 7, the amount of displacement can be accurately calculated. The positioning of the screen mask 2 and the substrate 1 can be performed with higher accuracy. Moreover, this process can be automated. In FIG. 1, the alignment mark 3 is provided so as to protrude for easy understanding, but needless to say, it may be recessed.

  Here, if the distance in which the printing stage 8 can be moved up and down is increased, the viewing range of the camera 7 can be expanded while the camera 7 is fixed. For example, when the alignment marks 3 and 4 are provided in the center portion. Even if it exists, the position of the shadow 6 of the alignment mark 3 and the alignment mark 4 can be made into the visual recognition range of a camera.

  After positioning the wafer 1 to be printed 1 and the screen mask 2 in this way, the printing stage 8 is raised to a predetermined position, a conductive paste as a printing material is supplied onto the screen mask 2, and a scraper is used. The conductive paste is filled in the opening window 9 of the screen mask 2 by moving in a direction parallel to the screen mask 2.

  Next, as shown in FIG. 2, when the squeegee 10 is brought into direct contact with the conductive paste, which is the printing material 11, and pressed, and is moved in parallel on the screen mask 2 so as not to contact the screen mask 2, Pressure is applied to the screen mask 2 from the squeegee 10 via the conductive paste 11, the screen mask 2 comes into contact with the wafer 1, and the conductive paste 11 is extruded through the opening window 9 to form a groove shape formed on the wafer 1. The recess 12 is filled to form an electrode.

  Moreover, the screen printing method of this invention can be used for the printing of the electrode pattern in formation of the multilayer structure electrode of a solar cell. A multi-layered electrode is formed by overlapping the same pattern as the electrode pattern of the first layer, and the line height is higher than the line width of the electrode, that is, the electrode has a high aspect ratio. Used. Therefore, the second and subsequent layers stacked on the first layer must be accurately printed on the first layer and the pattern. In such a case, the present invention is particularly effective.

  That is, in the screen printing method of the present invention, the substrate 1 is used as an electrode of a solar cell having an electrode pattern printed on the first layer, and the first layer electrode pattern is used as a positioning reference on the substrate side. As the positioning reference on the screen mask 2 side, an opening window 9 corresponding to the electrode pattern of the solar cell to be printed can be used.

In this case, first, a semiconductor substrate such as a silicon single crystal wafer on which the first layer electrode pattern is printed is prepared. Then, this substrate is fixed on the printing stage 8. Then, the screen mask 2 is set above the substrate.
Thereafter, light is irradiated from above the opening window 9 of the screen mask 2 by the light 5 to project a shadow of the opening window 9 of the screen mask 2 on the substrate. Then, the amount of displacement between the shadow and the first layer electrode pattern is calculated in the same manner as described above, and the substrate (printing stage) and the screen mask are positioned.

Thereafter, screen printing is performed on the first layer electrode pattern in the same manner as described above, and this is repeated at least once, whereby a multi-layer structure electrode can be obtained.
After positioning the substrate 1 and the screen mask 2 in this way, the electrode pattern is screen-printed, so that the positioning reference can be specifically set and positioning can be performed accurately even without the alignment mark. In addition, the electrode patterns having a multilayer structure can be accurately superimposed and printed. That is, an electrode having a multilayer structure in which the electrode width is not unnecessarily wide and shadow loss is reduced can be screen-printed.

  As described above, according to the present invention, in the screen printing method for performing printing on a printing material after positioning the printing material and the screen mask, the positioning is performed on the screen mask and the printing material by providing a positioning reference. Irradiating light from directly above the positioning reference on the side to project a shadow of the positioning reference on the screen mask side onto the substrate to be printed, so that the position of the shadow and the position of the positioning reference on the substrate side is eliminated. Since it is performed by relatively moving the printed material and the screen mask, it is possible to accurately position the screen mask and the printed material during printing, and it is possible to print the target print pattern on the printed material with high accuracy.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

(Example)
Using the screen printing method of the present invention, the electrode pattern of the solar cell is printed on a silicon single crystal wafer, and 50 wafers are continuously printed. The amount of deviation from this position was measured, and the change over time in the amount of deviation was evaluated.
First, 50 silicon single crystal wafers having a thickness of 300 μm and a diameter of 125 mm were prepared. Then, a groove-like recess having a width of 90 μm and a depth of 60 μm was formed on each wafer by grinding. In addition, two alignment marks as positioning references were provided near the center of the wafer.

The silicon single crystal wafer was fixed on the printing stage, and a screen mask having an opening window corresponding to the concave portion of the wafer and two alignment marks corresponding to the alignment mark on the wafer side was installed thereon.
Next, light is emitted from right above the alignment mark on the screen mask side by light, and the shadow of the alignment mark on the screen mask projected onto the wafer and the image of the alignment mark on the wafer side are captured by the camera and image processing is performed. Thus, the amount of deviation between the two was calculated.

Next, positioning was performed by moving the printing stage by the calculated amount of deviation.
Thereafter, the printing stage is raised to a predetermined position, a conductive paste having a viscosity of 100 pa · s is supplied onto the screen mask, the conductive paste is filled in the opening window of the screen mask with a scraper, and the squeegee is moved in parallel to move the wafer. The upper recess was filled with a conductive paste.

The result of the measured deviation is shown in FIG.
As shown in FIG. 4, in the screen printing method of the present invention, the amount of deviation between the print pattern printed on the substrate and the position of the print pattern to be originally printed is extremely small. Changes in the amount of deviation are also kept very small. In addition, it can be seen that printing is performed with high accuracy as compared with the shift amount by the conventional screen printing method of the comparative example described later.
Thus, it can be confirmed that the screen printing method of the present invention can accurately position the screen mask and the substrate during printing, and can accurately print the target print pattern on the substrate. It was.

(Comparative example)
As shown in FIG. 3, after the positioning of the printing material by the conventional positioning method of the printing material, the printing stage is moved directly below the screen mask, and the screen printing method is used to screen-print the printing pattern. An electrode pattern was printed on 50 wafers under the same conditions as in Example 1, and the same evaluation as in Example 1 was performed.
The result of the measured deviation is shown in FIG.
As shown in FIG. 4, it was found that the amount of deviation was larger than the result of the example, and that the amount of deviation increased with the passage of time. Therefore, maintenance is required at a predetermined cycle.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

It is a schematic explanatory drawing explaining an example of the screen printing method which concerns on this invention. It is a schematic explanatory drawing which shows a mode that the printing pattern is printed on to-be-printed material in screen printing. It is a schematic explanatory drawing explaining an example of the positioning method of the conventional to-be-printed material and a screen mask. It is the graph which showed the result of the Example and the comparative example.

Explanation of symbols

1 ... substrate, 2 ... screen mask, 3 ... alignment mark on the substrate side,
4 ... Screen mask side alignment mark, 5 ... Light, 6 ... Shadow,
7 ... Camera, 8 ... Printing stage, 9 ... Open window, 10 ... Squeegee,
11 ... printing material, 12 ... concave.

Claims (5)

  In the screen printing method of printing the printing pattern on the substrate through the opening window after positioning the screen mask having an opening window corresponding to the printing pattern and the substrate, the positioning includes the screen mask and A positioning reference is provided on the substrate, and a shadow of the positioning reference on the screen mask is projected onto the substrate by irradiating light from directly above the positioning reference on the screen mask, and the position of the shadow and the substrate A screen printing method comprising: moving the substrate and the screen mask relative to each other so as to eliminate a deviation from a positioning reference position on the side.   When positioning the printed material and the screen mask, the shadow and the positioning reference image on the printed material side are taken into an image processing unit, the image is processed to calculate the amount of deviation, and the printed material The screen printing method according to claim 1, wherein the screen mask is positioned by relatively moving the screen mask by the calculated displacement amount.   The screen printing method according to claim 1, wherein the printed material is an electrode of a solar cell.   The screen printing method according to claim 1, wherein an alignment mark is used as a positioning reference for the screen mask and the substrate. The printed material is an electrode of a solar cell on which an electrode pattern is printed on the first layer, and the first layer electrode pattern is used as the positioning reference on the printed material side, and the positioning reference on the screen mask side Using an opening window corresponding to the electrode pattern of the solar cell to be printed, and printing an electrode pattern of at least one layer on the electrode pattern of the first layer to form an electrode having a multilayer structure The screen printing method according to any one of claims 1 to 3.

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