JP5933821B2 - Screen printing machine - Google Patents

Description

  The present invention relates to a screen printer, and more particularly to a screen printer suitable for forming an electrode of a solar battery cell.

  The screen printing method is used for forming electrodes for solar cells and forming electrodes for various display devices such as liquid crystal display devices, plasma displays, and organic EL (Electro Luminescence) displays. In the screen printing method, a print mask on which a predetermined print pattern is formed is arranged on an upper part of the print object with a predetermined distance from the print object arranged on the printing stage. A paste containing an electrode material is supplied onto the printing mask.

  Here, the printing mask mainly comprises a mesh, an extruded emulsion, and a frame for reinforcing the whole. The printing pattern of the printing mask is formed by the presence or absence of emulsion in the plane of the printing mask. That is, no emulsion is placed on the mesh where the paste is printed in the plane of the print mask. On the contrary, the emulsion is placed on the mesh where the paste is not printed in the plane of the print mask. Thus, in the printing mask, whether or not the paste passes through the mesh is controlled by the presence or absence of the emulsion in the surface of the printing mask.

  When printing the paste, the paste supplied on the printing mask is spread thinly on the printing mask by a scraper and coated. The paste coated on the printing mask is supplied onto the object to be printed by passing through the mesh portion where the emulsion is not installed by sliding the squeegee on the printing mask. And the electrode is formed by baking the paste supplied on the printing object at a predetermined temperature corresponding to the electrode material contained in the paste.

  On the other hand, in order to use screen printing as a method with excellent practicality and mass productivity, various ideas have been made in addition to the above basic processing. Among them, the device for the scraper that evenly spreads the paste on the printing mask is positioned as one of the most important devices. When pursuing practicality and mass productivity, it is extremely important to repeat the same operation and action repeatedly. Immediately after one printing is performed, the paste supplied on the print mask is consumed for printing or is driven to the end on the print mask by a squeegee. For this reason, the paste becomes exhausted in the vicinity of the printing region to be printed.

  The scraper greatly contributes to replenishing the paste to the portion to be printed in a short time. Specifically, immediately after the completion of one printing, the scraper installed slightly downstream of the squeegee in the printing direction descends toward the printing mask in place of the rising of the squeegee from the printing mask. It moves in the direction opposite to the operation direction, that is, the printing direction. Of the paste repelled to the end on the print mask immediately after printing, the paste located between the squeegee and the scraper is supplied again near the print pattern on the print mask by this operation. A slight gap is pre-adjusted between the scraper and the printing mask. Thus, when the scraper is moved, the paste having a thickness corresponding to the gap remains uniformly on the print mask, and the paste is uniformly re-supplied on the print mask.

JP-A-11-227155

  By the way, in the formation of solar cells, screen printing using a paste having a low viscosity may be performed. Conventionally, when a paste having a low viscosity is printed on a solar cell substrate, a predetermined amount of paste is supplied onto the printing mask, and the paste is thinly spread and coated on the printing mask using a scraper. Then, the paste is printed on the solar cell substrate using a squeegee. The predetermined amount is an amount necessary for spreading the paste uniformly and thinly on the printing mask.

  When such a screen printing operation is repeatedly performed, in the case of a paste having a low viscosity, the paste protrudes and accumulates in a region outside the operation range of the scraper in the width direction of the scraper on the print mask. For this reason, the amount of paste for coating on the print mask is insufficient, and the paste coated on the print mask is faded, or as a result of areas where the paste is not coated, uniform printing cannot be performed, resulting in poor print fading. There was a problem of doing.

  Especially for pastes with low viscosity and high fluidity, the paste spreads to the periphery of the printing mask when coated, and the coating process is performed when continuous printing is performed by continuously performing the printing process with a squeegee and the coating process with a scraper. As a result, the amount of paste to be gradually decreased and a sufficient coating could not be obtained, and the shape of the printed pattern was impaired.

  In such a case, usually the viscosity of the paste is increased by increasing the ratio of the solid content constituting the paste so that the paste does not spread to the periphery of the print mask. However, depending on the paste material, increasing the solid content ratio may impair the functionality of the paste so that it does not function, and the viscosity of the paste cannot be adjusted.

  In the conventional screen printing as described above, the paste collecting ability depends on the shape and size of the scraper and the squeegee. That is, the recoverable range of the paste is determined depending on the shape and size of the scraper and squeegee. If for some reason the paste reaches an area beyond the range where the paste can be recovered, this amount of paste cannot be recovered, and wasteful paste that does not contribute to printing and is not recovered is generated. The generation of such a useless paste becomes more remarkable as the paste has a low viscosity and a property of spreading quickly due to its own weight.

  There may be a means to deal with such generation of useless paste by the size of the scraper and the squeegee. However, the increase in the size of the scraper and the squeegee has no effective meaning other than the recovery of the paste, and means that the apparatus becomes enormous. Therefore, it cannot be said that it is an effective means from the viewpoint of the entire apparatus.

  On the other hand, as a method for performing uniform printing, for example, in Patent Document 1, printing is performed by applying pressure on a screen corresponding to a printing area between both ends of a squeegee and a frame while applying pressure in accordance with the movement of the squeegee. A method has been proposed.

  However, according to the technique disclosed in Patent Document 1, the apparatus configuration and the operation of the apparatus become complicated, and the apparatus cost increases. Moreover, generation | occurrence | production of the useless paste which does not contribute to printing as mentioned above but is not collect | recovered cannot be eliminated.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a screen printer capable of continuous printing with good print quality without causing printing defects due to insufficient paste amount.

  In order to solve the above-described problems and achieve the object, a screen printing machine according to the present invention provides a paste coated on a print area of a print mask through the opening pattern provided in the print area. A screen printing machine for printing on a printing surface of a printing material disposed at a lower portion of the printing mask, wherein the upper surface of the printing mask is slid on the upper surface of the printing mask while being separated from the upper surface of the printing mask. A scraper that coats the printing area with the paste supplied to the sheet, and slides on the printing area coated with the paste in a direction opposite to the sliding direction of the scraper in contact with the upper surface of the printing mask. Accordingly, the squeegee for printing the paste on the printing surface through the opening pattern, and the squeegee on the upper surface of the printing mask. The upper surface of the printing mask and at least the side surface on the printing region side are provided in close contact with the outer peripheral side of the sliding region of the wrapper, and the paste protruding from the sliding region of the scraper is applied to the sliding region of the scraper. A bank member that rebounds to the side, and the bank member has an inclined surface that is lowered from the downstream side toward the upstream side in the sliding direction of the scraper on the upper surface, and when the scraper and the squeegee slide, the scraper The paste that protrudes from the sliding area and moves to the inclined surface moves to the upstream side due to the inclination of the inclined surface and moves to the sliding area of the scraper on the upper surface of the printing mask. To do.

  According to the present invention, it is possible to obtain a screen printer capable of continuous printing with good print quality without causing a printing defect due to insufficient paste amount.

1-1 is a figure which shows schematic structure of the photovoltaic cell in Embodiment 1 of this invention, and is a top view of the photovoltaic cell seen from the light-receiving surface side. 1-2 is a figure which shows schematic structure of the photovoltaic cell in Embodiment 1 of this invention, and is a bottom view of the photovoltaic cell seen from the light-receiving surface opposite side (back surface side). 1-3 is a figure which shows schematic structure of the photovoltaic cell in Embodiment 1, and is principal part sectional drawing in line segment AA of FIGS. 1-1. FIGS. 2-1 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-2 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-3 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-4 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-5 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-6 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-7 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-8 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-9 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIGS. 2-10 is principal part sectional drawing for demonstrating an example of the manufacturing process of the photovoltaic cell in Embodiment 1 of this invention. FIGS. FIG. 3A is a cross-sectional view illustrating the configuration of the screen printer according to the first embodiment of the present invention. FIG. 3-2 is a perspective view of the configuration of the screen printing machine according to the first embodiment of the present invention. FIG. 4A is a top view of the print mask of the screen printer according to the first embodiment of the present invention. FIG. 4-2 is a bottom view of the print mask of the screen printer according to the first embodiment of the present invention. 4-3 is principal part sectional drawing of the printing mask of the screen printer concerning Embodiment 1 of this invention. 4-4 is principal part sectional drawing of the printing mask of the screen printer concerning Embodiment 1 of this invention. FIG. 5-1 is a cross-sectional view illustrating a state at the start of coating when a dopant-containing paste is coated on a print mask by a scraper in the screen printing machine according to the first embodiment. 5-2 is sectional drawing which shows the state in the middle of the coating at the time of coating a dopant containing paste on a printing mask with a scraper in the screen printer concerning Embodiment 1. FIGS. 5-3 is sectional drawing which shows the state at the time of completion | finish of a coating at the time of coating a dopant containing paste on a printing mask with a scraper in the screen printer concerning Embodiment 1. FIGS. FIG. 6A is a top view illustrating a state at the start of coating when the dopant-containing paste is coated on the print mask by the scraper in the screen printing machine according to the first embodiment. FIG. 6-2 is a top view illustrating a state at the end of coating when the dopant-containing paste is coated on the print mask by the scraper in the screen printing machine according to the first embodiment. FIG. 7-1 is a cross-sectional view illustrating a state at the start of printing when the dopant-containing paste is printed on the p-type silicon substrate by the squeegee in the screen printing machine according to the first embodiment. FIG. 7-2 is a cross-sectional view illustrating a state in the middle of printing when the dopant-containing paste is printed on the p-type silicon substrate by the squeegee in the screen printing machine according to the first embodiment. FIG. 7-3 is a cross-sectional view illustrating a state at the end of printing when the dopant-containing paste is printed on the p-type silicon substrate by the squeegee in the screen printer according to the first embodiment. FIG. 8-1 is a top view illustrating a state at the start of printing when the dopant-containing paste is printed on the p-type silicon substrate by the squeegee in the screen printing machine according to the first embodiment. FIG. 8-2 is a top view illustrating a state at the end of printing when the dopant-containing paste is printed on the p-type silicon substrate by the squeegee in the screen printer according to the first embodiment. FIG. 9A is a schematic diagram illustrating a flow direction of excess dopant-containing paste protruding from the sliding region of the scraper in the width direction (X direction) of the scraper of the screen printing machine according to the first embodiment. FIG. 9-2 schematically shows a direction in which excess dopant-containing paste protruding from the sliding area of the scraper is circulated in the vicinity of the printing start position (coating end position) of the screen printing machine according to the first embodiment. FIG. FIG. 10 is a schematic cross-sectional view illustrating a state in which the printing mask and the rubber plate are bent during the printing operation of the dopant-containing paste of the screen printing machine according to the first embodiment. FIG. 11 is a top view of a printing mask for explaining a groove formed on the top surface of the bank member of the screen printing machine according to the first embodiment of the present invention. FIG. 12A is a perspective view of the configuration of the screen printing machine according to the second embodiment of the present invention. FIG. 12-2 is a cross-sectional view of a principal part of the print mask of the screen printer according to the second embodiment of the present invention. FIG. 13 is an enlarged perspective view of the main part showing the vicinity of the notch in the printing mask of the screen printing machine according to the second embodiment of the present invention. FIG. 14 is an enlarged perspective view of the main part showing the vicinity of the notch in the printing mask of the screen printing machine according to the second embodiment of the present invention.

  Hereinafter, embodiments of a screen printing machine according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment 1 FIG.
Below, the case where the screen printer concerning Embodiment 1 is applied to the manufacturing method of the photovoltaic cell using a dopant containing paste is demonstrated. Before describing the screen printer according to the first embodiment, first, a solar cell manufactured using the screen printer according to the first embodiment will be described. 1-1 is a figure which shows schematic structure of the photovoltaic cell 1 in Embodiment 1, FIG. 1-1 is a top view of the photovoltaic cell 1 seen from the light-receiving surface side, FIG. 1-2 is a bottom view of the solar battery cell 1 viewed from the side opposite to the light receiving surface (back surface side), and FIG. 1-3 is a cross-sectional view of the main part, which is essential for the line AA in FIG. FIG.

  In the solar cell 1 according to the first embodiment, an n-type impurity diffusion layer 3 is formed by phosphorous diffusion on the light receiving surface side of a semiconductor substrate 2 made of p-type silicon (hereinafter referred to as p-type silicon substrate 2). , A semiconductor substrate 11 having a pn junction is formed. Further, an antireflection film 4 made of, for example, a silicon nitride film (SiN film) is formed on the n-type impurity diffusion layer 3. As the semiconductor substrate 2, either a p-type single crystal silicon substrate or a p-type polycrystalline silicon substrate may be used. The semiconductor substrate 2 is not limited to a p-type silicon substrate, and an n-type polycrystalline silicon substrate or an n-type single crystal silicon substrate may be used.

  Further, on the light receiving surface side of the p-type silicon substrate 2, minute unevenness (texture) 2a constituting a texture structure for confining light is formed with a depth of about 10 μm. The minute unevenness (texture) 2 a has a structure that increases the area of the light receiving surface that absorbs light from the outside, suppresses the reflectance on the light receiving surface, and efficiently confines light in the solar battery cell 1.

  In the solar cell 1, two types of layers are formed as the n-type impurity diffusion layer 3 to form a selective emitter structure. That is, in the surface layer portion of the p-type silicon substrate 2 on the light-receiving surface side, a high-concentration impurity diffusion layer (low resistance) in which n-type impurities are diffused at a high concentration is formed in the lower region of the light-receiving surface-side electrode 12 and the vicinity thereof. A first n-type impurity diffusion layer 3a which is a diffusion layer) is formed. Further, in the surface layer portion on the light receiving surface side of the p-type silicon substrate 2, a low-concentration impurity diffusion layer (a high-concentration diffusion layer in which n-type impurities are diffused at a low concentration) A second n-type impurity diffusion layer 3b, which is a resistance diffusion layer), is formed.

The antireflection film 4 is made of a silicon nitride film (SiN film) that is an insulating film. The antireflection film 4 is not limited to the silicon nitride film (SiN film), and may be formed of an insulating film such as a silicon oxide film (SiO ₂ film) or a titanium oxide film (TiO ₂ film).

  In addition, a plurality of long and narrow surface silver grid electrodes 5 are arranged side by side on the light receiving surface side of the semiconductor substrate 11, and a surface silver bus electrode 6 electrically connected to the surface silver grid electrode 5 is substantially the same as the surface silver grid electrode 5. They are provided so as to be orthogonal to each other, and are respectively electrically connected to the n-type impurity diffusion layer 3 at the bottom portion. The front silver grid electrode 5 and the front silver bus electrode 6 are made of a silver material. The front silver grid electrode 5 and the front silver bus electrode 6 are formed by fire-through which will be described later, and a part thereof is embedded in the antireflection film 4.

  The front silver grid electrodes 5 are arranged substantially in parallel, for example, at a predetermined interval, and collect electricity generated within the semiconductor substrate 11. Moreover, the surface silver bus electrode 6 is arrange | positioned, for example per 2 photovoltaic cells, and takes out the electricity collected by the surface silver grid electrode 5 outside. The front silver grid electrode 5 and the front silver bus electrode 6 constitute a light receiving surface side electrode 12 which is a first electrode having a comb shape.

  The light receiving surface side electrode 12 described above is formed on the first n-type impurity diffusion layer 3a. Further, a region where the light receiving surface side electrode 12 is not formed and a region where the second n type impurity diffusion layer 3b is formed in the first n-type impurity diffusion layer 3a are light-receiving surfaces on which light is incident on the solar battery cell 1. .

  On the other hand, a back aluminum electrode 7 made of an aluminum material is provided on the back surface (surface opposite to the light receiving surface) of the semiconductor substrate 11 over substantially the whole area except for a part of the outer edge region. A back silver electrode 8 made of a silver material and extending in the same direction is provided. The back aluminum electrode 7 and the back silver electrode 8 constitute a back electrode 13 as a second electrode.

  Further, a p + layer (BSF (Back Surface Field)) 9 containing a high-concentration impurity is formed on the surface layer portion on the back surface (surface opposite to the light receiving surface) of the semiconductor substrate 11. The p + layer (BSF) 9 is provided to obtain the BSF effect, and the electron concentration of the p-type layer (semiconductor substrate 2) is increased by an electric field having a band structure so that electrons in the p-type layer (semiconductor substrate 2) do not disappear. Like that.

  Below, the manufacturing method of the photovoltaic cell 1 is demonstrated. FIGS. 2-1 to 2-10 are principal part cross-sectional views for explaining an example of the manufacturing process of solar cell 1 in the first embodiment of the present invention.

  First, for example, a p-type silicon substrate 2 is prepared as a semiconductor substrate (FIG. 2-1). The p-type silicon substrate 2 is obtained by cutting and slicing a single crystal silicon ingot or polycrystalline silicon ingot formed by cooling and solidifying molten silicon to a desired size and thickness with a wire saw using a band saw or a multi-wire saw. Because it is manufactured, the damage when slicing remains on the surface. In order to remove the damaged layer, the p-type silicon substrate 2 is first immersed in an acid or a heated alkaline solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution, and etched to a thickness of about 15 μm on the surface. As a result, a damaged region that occurs when the silicon substrate is cut out and exists near the surface of the p-type silicon substrate 2 is removed. Thereafter, the surface of the p-type silicon substrate 2 is washed with hydrofluoric acid and pure water.

  At the same time as the removal of damage or subsequent to the removal of damage, a fine unevenness 2a having a texture structure is formed on the surface of the p-type silicon substrate 2 on the light receiving surface side with a depth of about 10 μm (FIG. 2-2). For example, anisotropic etching of the p-type silicon substrate 2 is performed with a solution of about 80 ° C. to 90 ° C. obtained by adding several to several tens wt% of isopropyl alcohol (IPA) to a several wt% sodium hydroxide (NaOH) aqueous solution. Pyramidal micro unevenness (texture) is formed on the surface of the mold silicon substrate 2 on the light receiving surface side.

  In addition, in the manufacturing method of a solar cell, about the formation method and shape of a texture structure, it does not restrict | limit in particular. For example, an alkaline aqueous solution containing isopropyl alcohol or a method using acid etching mainly composed of a mixed solution of hydrofluoric acid and nitric acid, a method using a dry etching process such as reactive gas etching (RIE), etc. Either method can be used. For example, RIE may be used to form minute irregularities with a depth of, for example, 1 to 3 μm on the surface.

  Next, in order to form the first n-type impurity diffusion layer 3a which is a high-concentration impurity diffusion layer (low-resistance diffusion layer) in the selective emitter structure, a dopant-containing paste 21 as a diffusion source-containing coating agent is applied to a screen printing machine. It is applied and formed on one surface of the p-type silicon substrate 2 (FIGS. 2-3). Since the p-type silicon substrate 2 is used here, a dopant-containing paste 21 containing a phosphorus compound is used in order to use, for example, phosphorus as the n-type dopant. A screen printer used for printing the dopant-containing paste 21 will be described later. After printing of the dopant-containing paste 21, a drying process for drying the dopant-containing paste 21 is performed.

Next, the p-type silicon substrate 2 is put into a thermal diffusion furnace, and a first diffusion process (first heat treatment) that is a thermal diffusion process of the dopant (phosphorus) by the dopant-containing paste 21 is performed. This first diffusion process is the first stage of the two-stage diffusion process, phosphorus oxychloride (POCl ₃ ) is not used, and there is no diffusion source of dopant (phosphorus) other than the dopant-containing paste 21. . For this reason, thermal diffusion of the dopant (phosphorus) is performed only in the lower part of the region where the dopant-containing paste 21 is printed on the p-type silicon substrate 2. By this first diffusion process, the dopant (phosphorus) is thermally diffused from the dopant-containing paste 21 to a lower region of the printing region of the dopant-containing paste 21 on the surface of the p-type silicon substrate 2 to a high concentration (first diffusion concentration). First n-type impurity diffusion layer 3a is formed (FIGS. 2-4).

After the completion of the first diffusion step, a second diffusion step (second heat treatment) that is a thermal diffusion step of the dopant (phosphorus) with phosphorus oxychloride (POCl ₃ ) is subsequently performed. That is, the p-type silicon substrate 2 is continuously subjected to the second diffusion step after the first diffusion step in the same thermal diffusion furnace. This second diffusion process is the second stage of the two stages of diffusion processes. The second diffusion step is performed in the presence of phosphorus oxychloride (POCl ₃ ) gas in a thermal diffusion furnace. That is, in the second diffusion step, thermal diffusion is performed under atmospheric conditions including phosphorus oxychloride (POCl ₃ ) as a dopant (phosphorus) diffusion source.

  By this second diffusion step, a concentration lower than that of the first n-type impurity diffusion layer 3a in the region excluding the printing region of the dopant-containing paste 21 on the surface of the p-type silicon substrate 2, that is, the exposed region of the p-type silicon substrate 2 ( The second n-type impurity diffusion layer 3b is formed by thermally diffusing the dopant (phosphorus) to the second diffusion concentration (FIG. 2-5). Further, a glassy (phosphosilicate glass, PSG: Phospho-Silicate Glass) layer deposited on the surface during the diffusion process is formed on the surface of the p-type silicon substrate 2 immediately after the second diffusion step (not shown). ).

  Next, pn separation is performed (FIGS. 2-6). Since n-type impurity diffusion layer 3 is uniformly formed on the surface of p-type silicon substrate 2, the front surface and the back surface are in an electrically connected state. Therefore, when the back aluminum electrode 7 (p-type electrode) and the light-receiving surface side electrode 12 (n-type electrode) are formed as they are, the back aluminum electrode 7 (p-type electrode) and the light-receiving surface side electrode 12 ( n-type electrode) is electrically connected. In order to cut off this electrical connection, the second n-type impurity diffusion layer 3b formed in the end face region of the p-type silicon substrate 2 is removed by, for example, dry etching or laser to perform pn separation.

  Next, the vitreous layer and the dopant-containing paste formed on the surface of the p-type silicon substrate 2 in the second diffusion step by immersing the p-type silicon substrate 2 in, for example, a hydrofluoric acid solution and then performing a water washing treatment. The vitreous layer (the lump after the phosphorus compound is dissolved) which is a residue of 21 is removed (FIG. 2-7). Thus, a pn junction is formed by the semiconductor substrate 2 made of p-type silicon as the first conductivity type layer and the n-type impurity diffusion layer 3 as the second conductivity type layer formed on the light receiving surface side of the semiconductor substrate 2. As a result, a semiconductor substrate 11 having the structure shown in FIG.

  Further, as the n-type impurity diffusion layer 3, a selective emitter structure including a first n-type impurity diffusion layer 3a and a second n-type impurity diffusion layer 3b on the light receiving surface side of the p-type silicon substrate 2 is obtained. The sheet resistance on the light-receiving surface side of the semiconductor substrate 11 is, for example, 20 to 40Ω / □ for the first n-type impurity diffusion layer 3a serving as the lower region of the light-receiving surface-side electrode 12, and 80 for the second n-type impurity diffusion layer 3b serving as the light-receiving surface. ~ 120Ω / □.

Next, a silicon nitride (SiN) film, for example, having a uniform thickness, for example, a thickness of 60 to 80 nm is formed as the antireflection film 4 on the light receiving surface side (n-type impurity diffusion layer 3 side) of the semiconductor substrate 11 (see FIG. 2-8). The antireflection film 4 is formed using, for example, a plasma CVD method, and a mixed gas of silane (SiH ₄ ) gas and ammonia (NH ₃ ) gas is used as a raw material.

  Next, an electrode is formed by screen printing. First, a silver paste is applied in the shape of the back silver electrode 8 on the back surface side of the semiconductor substrate 11 by screen printing and then dried (FIG. 2-9). Next, after applying the aluminum paste 7a in the shape of the back aluminum electrode 7 on the back surface side of the semiconductor substrate 11 by screen printing, the aluminum paste is dried (FIG. 2-9).

  Next, the light-receiving surface side electrode 12 is produced (before firing). That is, after applying the silver paste 5a containing silver and glass frit to the shape of the front silver grid electrode 5 and the front silver bus electrode 6 on the antireflection film 4 which is the light receiving surface of the semiconductor substrate 11 by screen printing, The electrode material paste is dried (FIGS. 2-9). The light receiving surface side electrode 12 is formed in alignment with the first n-type impurity diffusion layer 3a.

  Thereafter, the electrode paste on the light-receiving surface side and the back surface side of the semiconductor substrate 11 is simultaneously fired in the atmosphere at a temperature of about 600 ° C. to 900 ° C., so that the glass contained in the silver paste on the front side of the semiconductor substrate 11 While the antireflective film 4 is melted by the material, the silver material comes into contact with the silicon and resolidifies. Thereby, the surface silver grid electrode 5 and the surface silver bus electrode 6 as the light-receiving surface side electrode 12 are obtained, and electrical connection between the light-receiving surface side electrode 12 and the silicon of the semiconductor substrate 11 is ensured (FIG. 2-10). . Such a process is called a fire-through method.

  On the back side of the semiconductor substrate 11, the silver paste comes into contact with silicon and resolidifies. Thereby, the back silver electrode 8 as the back surface side electrode 13 is obtained. Also, the aluminum paste reacts with the silicon of the semiconductor substrate 11 to obtain the back aluminum electrode 7, and the p + layer 9 is formed immediately below the back aluminum electrode 7. An aluminum alloy layer is formed between the back aluminum electrode 7 and the p + layer 9. In the figure, only the front silver grid electrode 5 and the back aluminum electrode 7 are shown, and the front silver bus electrode 6 and the back silver electrode 8 are not shown.

  By performing the above steps, the solar battery cell 1 according to the present embodiment shown in FIGS. 1-1 to 1-3 can be manufactured.

  Next, the screen printer according to the first embodiment used for printing the above-described dopant-containing paste 21 will be described. FIG. 3A is a sectional view of the configuration of the screen printing machine according to the first embodiment. FIG. 3-2 is a perspective view of the configuration of the screen printing machine according to the first embodiment. The screen printing machine includes a printing stage 31, a printing mask 32, a printing mask frame 33, a squeegee 34 that is a spatula-shaped jig, a scraper 35 that is a spatula-shaped jig, and a bank member 36. ing. In FIG. 3-2, only the positions of the printing mask 32 and the printing mask frame 33 at the start of the coating operation of the dopant-containing paste 21 by the scraper 35 are schematically shown.

  FIG. 4A is a top view of the print mask 32 of the screen printer according to the first embodiment. FIG. 4B is a bottom view of the print mask 32 of the screen printer according to the first embodiment. FIG. 4C is a cross-sectional view of the main part of the print mask 32 of the screen printing machine according to the first embodiment, corresponding to the AA cross section in FIG. FIG. 4-4 is a cross-sectional view of the main part of the print mask 32 according to the first embodiment, corresponding to the BB cross section in FIG. 3-2. Here, the surface on the printing mask 32 on which the dopant-containing paste 21 is supplied is the upper surface, and the surface on the side facing the p-type silicon substrate 2 is the lower surface. 4A, the positions of the squeegee 34 and the scraper 35 at the coat start position (print end position) are indicated by solid lines, and the positions of the squeegee 34 and the scraper 35 at the print start position (coat end position) are indicated by dotted lines.

  The printing stage 31 places and fixes the p-type silicon substrate 2 that is the printing object. The printing stage 31 positions and fixes the p-type silicon substrate 2 by, for example, vacuum-sucking the p-type silicon substrate 2 placed on the upper surface (stage surface) thereof.

  A rectangular print mask 32 is disposed on the p-type silicon substrate 2 fixed on the printing stage 31 with a predetermined distance from the upper surface (printed surface) of the p-type silicon substrate 2. In the printing mask 32, a metal mesh is stretched and supported with a predetermined tension between printing mask frames 33 made of, for example, an aluminum alloy. That is, the print mask frame 33 is provided along the outer periphery of the print mask 32 at the outer peripheral edge of the print mask 32 to hold the metal mesh. In the metal mesh, a photosensitive resin film (emulsion) is applied to a portion excluding an opening (not shown) corresponding to the printing pattern. The printing mask 32 and the printing stage 31 are positioned by alignment markers provided on each.

  Above the printing mask 32, a squeegee 34 and a scraper 35 are provided so as to be moved up and down by a driving means (not shown) and movable in a predetermined sliding direction (Y direction in FIG. 3-2). 3-2, the moving direction of the scraper 35 when the dopant-containing paste 21 is coated by the scraper 35 is defined as a coating direction Y1. Further, the sliding direction of the squeegee 34 when the dopant-containing paste 21 is printed by the squeegee 34 is defined as a printing direction Y2. The printing direction Y <b> 2 is parallel to the extending direction of the pair of frame portions along the Y direction in the printing mask frame 33. The squeegee 34 is arranged in a direction substantially parallel to the scraper 35 on the downstream side in the sliding direction of the scraper 35 in the printing direction Y2 with a predetermined distance from the scraper 35.

  The X direction is the width direction of the squeegee 34 and the scraper 35. The width direction of the squeegee 34 and the scraper 35 is a direction substantially orthogonal to the Y direction in the surface direction of the printing mask 32. Further, the width dimension of the squeegee 34 is substantially equal to the pattern printing area P in the printing mask 32, or the both ends of the squeegee 34 protrude from the pattern printing area P in the X direction. The pattern printing region P is a region in which an opening corresponding to the printing pattern is provided in the emulsion and the dopant-containing paste 21 is printed on the p-type silicon substrate 2 that is the printing object. The width dimension of the scraper 35 is longer than the width dimension of the squeegee 34 so that both ends protrude from the squeegee 34 in the X direction. A portion of the scraper 35 that protrudes from the squeegee 34 is a bent portion 35a that is bent in the printing direction Y2. The Z direction is the ascending / descending direction of the squeegee 34 and the scraper 35.

  The region including the pattern printing region P on the printing mask 32 is thinly coated with the dopant-containing paste 21 by the scraper 35, and the printing in FIG. 3-2 is performed with a predetermined pressing force applied to the printing mask 32 by the squeegee 34. By sliding the squeegee 34 on the pattern printing region P along the direction Y2, the dopant-containing paste 21 is pushed out to the p-type silicon substrate 2 through the opening of the printing mask 32, and a desired pattern is formed on the p-type silicon substrate. 2 is printed.

  Here, on the upper surface of the printing mask 32, two bank members 36 are arranged in a direction parallel to the printing direction Y2 in a region outside the sliding region of the scraper 35 in the width direction (X direction) of the scraper 35. It is arranged in close contact with the upper surface of 32. That is, two bank members 36 are arranged in the direction parallel to the extending direction of the frame portion adjacent to the inner walls of the pair of frame portions facing each other in the X direction in the print mask frame 33.

  The bank member 36 has a flat inclined surface whose upper surface decreases in height from a printing start position (coating end position) by the squeegee 34 toward a coating start position (printing end position) by the scraper 35. That is, the inclined surface is an inclined surface that decreases from the downstream side toward the upstream side in the sliding direction of the scraper 35. The bank member 36 has a substantially rectangular planar shape and a substantially trapezoidal longitudinal section. Further, the bottom surface portion of the bank member 36 that contacts the upper surface of the printing mask 32 is constituted by a rubber plate 37 having a substantially uniform thickness. On the other hand, portions other than the bottom surface portion of the bank member 36 are made of resin. The dimensions of the bank member 36 are, for example, a height of 20 mm at the end on the print start position (coat end position) side, a height of 8 mm at the end on the coat start position (print end position) side, and a width of 24 mm.

  The planar shape of the bank member 36 in the surface direction of the printing mask 32 is not limited to a substantially rectangular shape. That is, it is not essential that the side wall of the bank member 36 on the sliding region side of the scraper 35 is a flat surface parallel to the Y direction. As will be described later, excess dopant-containing paste 21 that is disposed on the outer peripheral side of the sliding area of the scraper 35 in the surface direction of the printing mask 32 and protrudes from the scraper 35 and flows in the direction of the printing mask frame 33 is transferred to the pattern printing area P. Any shape that can bounce off the side surface on the side and return to the sliding region of the scraper 35 may be used.

  Next, the printing operation of this screen printer will be described. FIGS. 5-1 to 5-3 are cross-sectional views showing the state of the screen printer when the dopant-containing paste 21 is coated on the print mask 32 by the scraper 35, and FIG. 5-2 shows a state during coating, and FIG. 5-3 shows a state at the end of coating. FIGS. 6A and 6B are top views showing the state of the screen printer when the dopant-containing paste 21 is coated on the print mask 32 by the scraper 35, and FIG. 6-2 shows the state at the end of the coating.

  FIGS. 7-1 to 7-3 are cross-sectional views showing the state of the screen printing machine when the dopant-containing paste 21 is printed on the p-type silicon substrate 2 by the squeegee 34, and FIG. FIG. 7-2 shows a state during printing, and FIG. 7-3 shows a state at the end of printing. FIGS. 8A and 8B are top views showing the state of the screen printing machine when the dopant-containing paste 21 is printed on the p-type silicon substrate 2 by the squeegee 34. FIG. FIG. 8-2 shows a state at the end of printing.

  First, in a state where both the squeegee 34 and the scraper 35 are disposed above the print mask 32 at the coat start position (print end position), the space between the coat start position of the scraper 35 on the upper surface of the print mask 32 and the pattern print region P Is supplied with a dopant-containing paste 21. The supply of the dopant-containing paste 21 onto the printing mask 32 may be performed manually or automatically. The amount of the dopant-containing paste 21 placed on the printing mask 32 is determined to be an amount that can uniformly cover the pattern printing region P of the printing mask 32 at the time of coating each of the plurality of p-type silicon substrates 2 that perform printing processing continuously. Is done.

  The dopant-containing paste 21 is a paste made of a resin containing several percent of phosphorus and its compound and an organic solvent. Since the content ratio of solid components is low, the viscosity is low and the fluidity is high. When the content ratio of the solid component (phosphorus) is increased in order to increase the viscosity of the dopant-containing paste 21, it is difficult to adjust the sheet resistance of the p-type silicon substrate 2 in which the dopant has diffused from the dopant-containing paste 21. Further, if the dopant-containing paste 21 contains other solid components, the other solid components diffuse into the p-type silicon substrate 2 and the impurity concentration of the first n-type impurity diffusion layer 3a increases, and the characteristics of the solar cell element are improved. Deteriorating factor. Therefore, it is difficult to increase the viscosity of the dopant-containing paste 21, and it is necessary to use the dopant-containing paste 21 having high fluidity. In the first embodiment, for example, a dopant-containing paste 21 paste having a viscosity of 60 Pa · s is used.

  Next, the scraper 35 is lowered onto the upper surface of the printing mask 32 along the Z-axis direction by the driving mechanism (FIGS. 5A and 5B). The scraper 35 is disposed on the upper surface of the print mask 32 in a non-contact state with the upper surface of the print mask 32 so as to have a slight gap with respect to the upper surface of the print mask 32. The distance between the scraper 35 and the printing mask 32 may be any suitable distance that can uniformly coat the upper surface of the printing mask 32 with the dopant-containing paste 21 necessary for printing. For example, a gap of several tens to several hundreds of μm is provided.

  Next, while the predetermined pressure is applied to the scraper 35 in the Z-axis direction by the drive mechanism, the scraper 35 is placed in the printing start position along the coating direction Y1 while maintaining a gap of a predetermined distance from the upper surface of the printing mask 32. Move to (coating end position). Thereby, the dopant-containing paste 21 is thinly printed on the upper surface of the print mask 32 including the pattern printing region P, and the upper surface of the print mask 32 is coated (covered) with the dopant-containing paste 21 (FIGS. 5-2 and 5-3). 6-2).

  At this time, the extra dopant-containing paste 21 that protrudes from the scraper 35 in the width direction (X direction) of the scraper 35 does not reach the scraper 35 in the width direction (X direction) of the scraper 35 and is printed in the direction of the printing mask frame 33. It flows on the upper surface. That is, the excess dopant-containing paste 21 that protrudes from the scraper 35 flows in a region outside the sliding region of the scraper 35 in the width direction (X direction) of the scraper 35. The extra dopant-containing paste 21 that protrudes from the scraper 35 in the width direction (X direction) of the scraper 35 is not limited to the paste that flows in the X direction, but also protrudes into a region adjacent to the sliding region of the scraper 35 in the X direction. The dopant containing paste 21 is meant.

  The extra dopant-containing paste 21 is an extra amount in the printing operation in progress, but is supplied in advance as an amount necessary for printing in the subsequent coating and printing operations in continuous printing. Therefore, when the printing process is repeated while the dopant-containing paste 21 flows and accumulates in a region outside the sliding region of the scraper 35, the dopant-containing paste 21 used for printing decreases, and the dopant-containing paste 21 As a result, the coat fading occurs, resulting in poor printing.

  Therefore, in the screen printing machine according to the present embodiment, the bank member 36 is installed in the vicinity of the sliding area of the scraper 35 in the width direction (X direction) of the scraper 35 on the upper surface of the printing mask. Then, the excess dopant-containing paste 21 that protrudes from the scraper 35 in the width direction (X direction) of the scraper 35 and flows in the direction of the printing mask frame 33 hits the side wall on the sliding region side of the scraper 35 of the bank member 36 and is bounced back. It is returned to the inner area of the print mask 32.

  That is, the excess dopant-containing paste 21 that has flowed in the direction of the print mask frame 33 bounces off against the side wall of the bank member 36 and flows to the inner region of the print mask 32 as indicated by an arrow C in FIG. Thereby, excess dopant-containing paste 21 is circulated and supplied into the sliding area of the scraper 35 and the pattern printing area P. FIG. 9A is a diagram schematically illustrating a direction in which excess dopant-containing paste 21 protruding from the sliding region of the scraper 35 in the width direction (X direction) of the scraper 35 is circulated and supplied. And the dopant containing paste 21 returned in the sliding area | region of the scraper 35 and the pattern printing area | region P is used for coating operation | movement as it is in the next coating operation | movement.

  Further, as shown in FIG. 6B, when the scraper 35 moves to the printing start position (coating end position), the extra dopant-containing paste 21 protruding from the scraper 35 in the width direction (X direction) of the scraper 35 In the vicinity of the print start position (coat end position) position, it moves onto the bank member 36 due to the momentum of the flow (to the biasing force by the scraper 35). FIG. 9B is a diagram schematically illustrating a direction in which excess dopant-containing paste 21 protruding from the sliding region of the scraper 35 is circulated and supplied in the vicinity of the print start position (coat end position). Excess dopant-containing paste 21 moves onto bank member 36 as shown by arrow D in FIG.

  Here, the upper surface of the bank member 36 is a flat inclined surface whose height decreases in the Y direction from the print start position (coat end position) toward the coat start position (print end position). For this reason, the dopant-containing paste 21 that has moved onto the bank member 36 uses the inclination of the upper surface of the bank member 36 to coat the upper surface of the bank member 36 as indicated by the arrow E in FIG. Move to the (printing end position) direction.

The dopant-containing paste 21 that has moved the upper surface of the bank member 36 in the direction of the coat start position (print end position) is the coat start position (print end position) of the pair of frame portions facing each other in the Y direction in the print mask frame 33. It hits the inner wall of the frame on the side and flows on the print mask 32 as shown by the arrow F in FIG. The dopant-containing paste 21 that has flowed onto the printing mask 32 flows into the sliding area of the scraper 35 and into the pattern printing area P. Thus, excess dopant containing paste 21 protruding from the scraper 35 at the print start position (coating end position) near neighbor is efficiently coated starting position side to the circulation supplying the sliding region of the scraper 35 (reflux). Further, a slope that decreases toward the pattern printing region P may be provided on the upstream side in the sliding direction of the scraper 35 on the upper surface of the bank member 36. As a result, the dopant-containing paste 21 that has flowed upstream on the top surface of the bank member can easily flow on the printing mask 32.

  And the dopant containing paste 21 returned in the sliding area | region of the scraper 35 is used for coating operation | movement as it is in the next coating operation | movement. In the next coating operation, the dopant-containing paste 21 that has moved to the bank member 36 side from the pattern printing region P in the sliding region of the scraper 35 is scraped to the pattern printing region P by the bent portion 35.

  Note that it is preferable to provide a step or the like that is one step higher than the upper surface of the bank member 36 on the outer peripheral edge of the upper surface of the bank member 36 on the print mask frame 33 side. Thereby, when the dopant containing paste 21 flows through the upper surface of the bank member 36, it is possible to prevent the dopant containing paste 21 from flowing between the bank member 36, the print mask frame 33, and the bank member 36.

  Further, as shown in FIG. 9A, in order to obtain the effect of circulatingly supplying the dopant-containing paste 21 on the upper surface of the printing mask 32, it is not essential that the upper surface of the bank member 36 is a slope.

  Next, when the scraper 35 moves to the printing start position (coating end position) and the coating operation of the dopant-containing paste 21 is completed, the pressure applied to the scraper 35 is released by the driving mechanism, and the scraper 35 is further removed from the printing mask 32. To the Z-axis direction.

  Next, the drive mechanism lowers the squeegee 34 along the Z axis on the print mask 32 (FIGS. 7-1 and 8-1). In this state, a predetermined pressure is applied to the squeegee 34 in the Z-axis direction, and the tip of the squeegee 34 is slid to the coat start position (print end position) along the print direction Y2 while contacting the top surface of the print mask 32. . Thereby, a part of the dopant-containing paste 21 thinly coated on the upper surface of the printing mask 32 passes through the metal mesh in the opening of the printing mask 32 and is printed on the surface of the p-type silicon substrate 2 (FIG. 7-2). 7-3, FIG. 8-2). Further, the dopant-containing paste 21 that is not printed on the surface of the p-type silicon substrate 2 is scraped by the squeegee 34 toward the coating start position (printing end position).

  At this time, a part of the excess dopant-containing paste 21 that protrudes from the squeegee 34 in the width direction (X direction) of the squeegee 34 does not reach the scraper 35 in the width direction (X direction) of the squeegee 34. To flow. That is, a part of the excess dopant-containing paste 21 that protrudes from the squeegee 34 flows in a region outside the sliding region of the scraper 35 in the width direction (X direction) of the squeegee 34. The extra dopant-containing paste 21 is an extra amount in the printing operation in progress, but is supplied in advance as an amount necessary for printing in the subsequent coating and printing operations in continuous printing. Therefore, when the printing process is repeated while the dopant-containing paste 21 flows and accumulates in a region outside the sliding region of the scraper 35, the dopant-containing paste 21 used for printing decreases, and the dopant-containing paste 21 As a result, the coat fading occurs, resulting in poor printing. A part of the extra dopant-containing paste 21 remains in the sliding area of the scraper 35.

  Here, in the screen printing machine according to the present embodiment, as described above, the bank member 36 is installed in the vicinity of the sliding area of the scraper 35 in the width direction (X direction) of the scraper 35. For this reason, the excess dopant-containing paste 21 that flows in the direction of the print mask frame 33 outside the sliding area of the scraper 35 is bounced off against the side wall of the bank member 36 on the sliding area side of the scraper 35 and is rebounded. Returned to

  That is, the excess dopant-containing paste 21 that has flowed in the direction of the print mask frame 33 outside the sliding area of the scraper 35 hits the side wall of the bank member 36 as shown by an arrow C in FIG. 32 to the inner region. Thereby, excess dopant-containing paste 21 is circulated and supplied into the sliding area of the scraper 35 and the pattern printing area P. And the dopant containing paste 21 returned in the sliding area | region of the scraper 35 and the pattern printing area | region P is used for coating operation | movement as it is in the next coating operation | movement. Further, the dopant-containing paste 21 scraped to the print start position (coating end position) side by the squeegee 34 within the moving area of the squeegee 34 is also used for the coating operation as it is in the next coating operation.

  Further, even during printing with the squeegee 34, as in the case of the coating operation with the scraper 35 described above, a part of the excess dopant-containing paste 21 protruding from the squeegee 34 in the width direction (X direction) of the squeegee 34 flows. It moves on the bank member 36 by the momentum (to the urging force by the squeegee 34).

  Then, the dopant-containing paste 21 that has moved onto the bank member 36 uses the inclination of the upper surface of the bank member 36 to coat the upper surface of the bank member 36 as indicated by the arrow E in FIG. End direction) and flows on the print mask 32 as indicated by an arrow F in FIG. The dopant-containing paste 21 that has flowed onto the printing mask 32 flows into the sliding area of the scraper 35 and into the pattern printing area P. As a result, excess dopant-containing paste 21 protruding from the squeegee 34 during printing by the squeegee 34 is efficiently circulated and supplied to the coat start position side in the sliding area of the scraper 35.

  Further, in screen printing, a squeegee is slid by placing a printing mask in a state of floating from a printing surface in order to perform stable printing. That is, if printing is performed in a state where the entire printing mask is in contact with the printing surface in advance, the printing mask must be peeled off from the printing surface after printing. However, when such a process is performed, the state of the printed film becomes unstable, for example, the printed film already printed on the surface to be printed is peeled off together with the print mask. For this reason, in order to perform stable printing, the printing mask is set in a non-contact state with the printing surface while slightly floating from the printing surface.

  On the other hand, since the printing mask is set in a state slightly lifted from the printing surface, only the portion pressed by the squeegee contacts the printing surface in the printing mask. Therefore, when the squeegee 34 slides, the printing mask 32 is pulled down from the printing mask frame 33 toward the printing surface (p-type silicon substrate 2) around the contact portion with the squeegee 34. When the bank member 36 is disposed, the print mask 32 is bent downward in this manner, so that a slight gap is generated between the bottom surface of the bank member 36 and the print mask 32. When this gap occurs, a part of the extra dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 during the printing operation using the squeegee 34 is printed through this gap. It flows to the mask frame 33 side and accumulates at the inner end of the print mask frame 33.

  Therefore, in the screen printer according to the first embodiment, as shown in FIGS. 4-2 to 4-4, the dopant-containing paste 21 is kept in close contact with the bottom surface of the bank member 36 and the top surface of the printing mask 32. A rubber plate 37 is disposed as a deformable member having flexibility to be bent by its own weight while being in close contact with the upper surface of the print mask 32 along the deflection of the print mask 32 during the printing operation. This rubber plate 37 is bent by its own weight along the bent printing mask 32 when the entire printing mask 32 is bent in the direction of the p-type silicon substrate 2 during the printing operation of the dopant-containing paste 21. As shown in FIG. 10, it adheres to the upper surface of the bent printing mask 32. Thereby, also in the printing operation of the dopant-containing paste 21, the bottom surface of the bank member 36 and the top surface of the printing mask 32 are in close contact with each other, and the generation of a gap between the bottom surface of the bank member 36 and the printing mask 32 is prevented. FIG. 10 is a schematic cross-sectional view showing a state where the printing mask 32 and the rubber plate 37 are bent during the printing operation of the dopant-containing paste 21.

  Therefore, in the screen printer according to the first embodiment, the extra dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 during the printing operation of the dopant-containing paste 21 is caused by the bent printing mask 32. , And is returned to the sliding area of the scraper 35 by hitting the rubber plate 37 that is in close contact with the upper surface of the printing mask 32. This prevents the dopant-containing paste 21 from flowing through the gap between the bottom surface of the bank member 36 and the print mask 32 to the print mask frame 33 side.

  As described above, in the screen printing machine according to the first embodiment, the printing mask is caused by the generation of the dopant-containing paste 21 that flows to the printing mask frame 33 side through the gap between the bottom surface of the bank member 36 and the printing mask 32. A reduction in the amount of dopant-containing paste 21 required in the 32 printing areas is prevented.

  Usually, the amount that the printing mask 32 is bent by being pulled in the direction of the printing surface during the coating operation and the printing operation is about 2 mm. Therefore, the thickness of the rubber plate 37 is greater than the height of the extra dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 and reaches the bank member 36 during the printing operation. It only has to be. This prevents the dopant-containing paste 21 from flowing into the gap between the upper surface of the rubber plate 37 and the lower surface of the main body of the bank member 36. The thickness of such a rubber plate 37 includes the amount of dopant-containing paste 21 supplied to the print mask 32 during a series of printing operations, the viscosity (fluidity) of the dopant-containing paste 21, the distance between the scraper 35 and the bank member 36, and the like. What is necessary is just to set suitably according to these conditions.

  Here, the configuration in which the rubber plate 37 is disposed on the entire bottom surface of the bank member 36 is described, but the shape of the rubber plate 37 is not limited to this. If the rubber plate 37 covers at least a part of the moving area of the squeegee 34 in the printing direction Y2, the above effect can be obtained in that part. Further, in consideration of the flow of the extra dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 and reaches the bank member 36, it is further expanded from the sliding region of the scraper 35 in the printing direction Y <b> 2. By covering the region, the above effect can be obtained more reliably.

  On the other hand, in the shape of the rubber plate 37, the dimension in the width direction (X direction) is an extra dopant-containing paste that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 during the printing operation of the dopant-containing paste 21. If it can prevent that 21 flows to the printing mask frame 33 side, it will not specifically limit.

  Here, the configuration in which the rubber plate 37 is disposed on the bottom surface of the bank member 36 as the deforming member is described, but a member other than the rubber plate 37 may be disposed on the bottom surface of the bank member 36 as the deforming member. That is, even in the printing operation of the dopant-containing paste 21, the bottom surface of the bank member 36 and the top surface of the printing mask 32 can be brought into close contact with each other to prevent the generation of a gap between the bottom surface of the bank member 36 and the printing mask 32. I just need it.

  Further, it is preferable that the side surface of the deformable member on the scraper 35 side has water repellency or is subjected to water repellency treatment.

  Next, when the squeegee 34 moves to the coating start position (printing end position) and the printing operation of the dopant-containing paste 21 is completed, the pressure applied to the squeegee 34 is released by the driving mechanism, and the squeegee 34 is further removed from the printing mask 32. To the Z-axis direction. By performing the above operations, the printing process of the dopant-containing paste 21 on one p-type silicon substrate 2 is completed.

  Then, by repeating the above operation, the dopant-containing paste 21 is continuously printed on the plurality of p-type silicon substrates 2 without supplying a new dopant-containing paste 21.

  On the upper surface of the bank member 36, for example, as shown in FIG. 11, a groove 38 extending in the direction (Y direction) from the printing start position (coat end position) to the coat start position (print end position) is formed. It may be. As a result, the dopant-containing paste 21 that has moved to the upper surface of the bank member 36 enters the groove portion 38 and flows along the groove portion 38 on the upper surface of the bank member 36, thereby coating the dopant-containing paste 21 at the coating start position (printing end position). Can be guided to the side. FIG. 11 is a top view of the print mask 32 for explaining the groove 38 formed on the top surface of the bank member 36.

  Further, in the screen printing machine according to the first embodiment described above, in addition to using the inclination of the upper surface of the bank member 36, the paste on the upper surface of the bank member 36 is used as a spatula-like jig such as a squeegee. May be used to force down.

  As described above, in the screen printing machine according to the first embodiment, on the upper surface of the printing mask 32, the bank member 36 is disposed in an area outside the sliding area of the scraper 35 in the width direction (X direction) of the scraper 35. Has been placed. As a result, excess dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction (X direction) of the scraper 35 is bounced off against the side wall of the bank member 36, and within the sliding region of the scraper 35 and the pattern printing region. Circulatingly supplied into P.

  Further, in the screen printing machine according to the first embodiment, excess dopant-containing paste 21 protruding from the scraper 35 in the width direction (X direction) of the scraper 35 flows in the vicinity of the printing start position (coating end position). The top surface of the bank member 36 is moved in the direction of the coat start position (print end position) by using the inclination of the top surface of the bank member 36 by the momentum, and the coat start position (print end position) side Are circulated and fed into the sliding area of the scraper 35 and the pattern printing area P.

  Therefore, according to the screen printer according to the first embodiment, excess dopant-containing paste 21 that protrudes from the sliding region of the scraper 35 in the width direction of the scraper 35 is contained in the sliding region of the scraper 35 and in the pattern printing region P. Thus, the dopant-containing paste 21 can be efficiently used effectively. Thereby, according to the screen printer concerning Embodiment 1, even during the continuous printing process, the amount of the dopant-containing paste 21 necessary for printing in order to coat the print mask 32 can be ensured. Continuous printing can be performed with good print quality by preventing defects due to printing blur due to shortage.

  In addition, according to the screen printing machine concerning such Embodiment 1, continuous printing was implemented with respect to 1000 p-type silicon substrates 2 in the actual experiment, without adding the dopant containing paste 21 on the way. Even in this case, it was confirmed that no defects caused by printing blur occurred. In the case of a screen printing machine having the same configuration except that the bank member 36 is not disposed, the number of p-type silicon substrates 2 that could be continuously printed without causing defects due to printing blurring was 20. From this, the screen printing machine according to the first embodiment has an effect of increasing the number of continuous prints while maintaining good print quality by 50 times.

Embodiment 2. FIG.
In the second embodiment, the bank member 36 installed on the printing mask 32 shows a more suitable shape for circulating the dopant-containing paste 21. FIG. 12A is a perspective view of the configuration of the screen printing machine according to the second embodiment. FIG. 12-2 is a cross-sectional view of a principal part of a print mask of the screen printing machine according to the second embodiment, and corresponds to a BB cross section in FIG. The screen printing machine according to the second embodiment is different from the screen printing machine according to the first embodiment in that part of the upper surface of the bank member 36 in the vicinity of both end portions in the moving direction (Y direction) of the scraper 35 and the squeegee 34. In addition, a guide wall (convex portion) 40 that has a notch 41 and a notch 42 and protrudes upward is provided. FIG. 13 is an enlarged perspective view of the main part showing the vicinity of the notch 41. FIG. 14 is an enlarged perspective view of the main part showing the vicinity of the notch 42.

  Containing dopant that has moved to the upper surface of the bank member 36 by providing a guide wall 40 along the upper surface of the bank member 36 at the upper end of the inner wall of the printing mask 32 (on the pattern printing region P side) on the upper surface of the bank member 36 A path of movement of the paste 21 is formed. That is, the dopant-containing paste 21 that has moved to the upper surface of the bank member 36 can move along the guide wall 40 in the direction of the coating start position (printing end position) on the upper surface of the bank member 36. Thereby, the dopant containing paste 21 which moved to the upper surface of the bank member 36 can be smoothly guided in the direction of the coating start position (printing end position).

  A notch 41 is provided in a part of the guide wall 40 on the printing start position (coating end position) side in the moving direction (Y direction) of the scraper 35 and the squeegee 34. Accordingly, the dopant-containing paste 21 that protrudes from the scraper 35 in the width direction and reaches the bank member 36 flows in the direction indicated by the arrow in FIG. 13 and is easily moved to the bank member 36. The dopant-containing paste 21 that has moved from the notch 41 to the top surface of the bank member 36 causes the top surface of the bank member 36 along the guide wall 40 in the direction of the coating start position (printing end position) due to the inclination of the top surface of the bank member 36. Moving.

  Further, a notch portion 42 is provided on a part of the guide wall 40 on the coat start position (print end position) side in the moving direction (Y direction) of the scraper 35 and the squeegee 34. Thereby, the dopant-containing paste 21 that has moved on the top surface of the bank member 36 in the direction of the coating start position (printing end position) flows in the direction indicated by the arrow in FIG. 14 and flows from the notch portion 42 onto the printing mask 32. The dopant-containing paste 21 can easily flow from the upper surface of the bank member 36 onto the printing mask 32. Thereby, the dopant-containing paste 21 is efficiently circulated and supplied onto the print mask 32.

  The notched portion 42 is provided closer to the coating start position (printing end position) than the coating start position (printing end position) of the scraper 35, so that the dopant-containing paste 21 is reliably placed in the sliding region of the scraper 35 and The pattern printing area P is circulated and supplied.

  Note that a groove portion 38 may be formed on the upper surface of the bank member 36 as shown in the first embodiment. As a result, the dopant-containing paste 21 that has moved from the notch 41 to the top surface of the bank member 36 can be surely flow on the top surface of the bank member 36 along the groove 38, in addition to being guided to the guide wall 40, The dopant-containing paste 21 can be efficiently induced.

  As described above, according to the screen printing machine according to the second embodiment, by providing the guide wall 40 on the bank member 36, the dopant-containing paste 21 that has moved to the upper surface of the bank member 36 is applied to the coating start position (print end position). ) Can be smoothly guided in the direction. As a result, the dopant-containing paste 21 that has moved onto the bank member 36 in the vicinity of the printing start position (coating end position) is efficiently contained in the sliding area of the scraper 35 on the coating start position (printing end position) side and in the pattern printing area P. Can be circulated to supply.

  Therefore, according to the screen printer according to the second embodiment, the amount of the dopant-containing paste 21 necessary for printing in order to coat the print mask 32 even during the continuous printing process can be secured. Continuous printing can be performed with good print quality by preventing defects due to printing blur due to shortage.

Embodiment 3 FIG.
In the third embodiment, a paste that can be continuously printed with good print quality by being circulated by the screen printer according to the above-described embodiment will be described. In the screen printing machine, by performing a coating operation to spread the paste thinly on the printing mask using a scraper, the paste protruding from the scraper moves to an end region on the printing mask. In the screen printing machine according to the above-described embodiment, the paste moving to the end region on the printing mask is moved onto the bank member 36 as described above, and the printing mask 32 is used by using the inclination of the upper surface of the bank member 36. It is possible to move (circulate) to the upper coat start position (print end position).

  As such a paste that can be circulated, a paste having a low viscosity and a high fluidity is suitable. By using a paste having a low viscosity and a high fluidity, the paste can be moved and reliably circulated using the inclination of the upper surface of the bank member 36.

  As such a paste having low viscosity and high fluidity, for example, a paste having a viscosity of 80 Pa · s or less is preferable. By using a paste having such a viscosity, it is possible to reliably circulate the paste using the bank member 36, and in continuous screen printing, the amount of paste required for the coating operation by the scraper 35 is as follows. It can be secured without supplying additional new paste.

  As the paste viscosity becomes higher than 80 Pa · s, the fluidity of the paste gradually decreases, and the paste cannot be circulated (moved) using the slope of the bank member 36. For this reason, in continuous screen printing, the amount of paste to be thinly spread on the print mask 32 by the scraper 35 is insufficient, and as a result, the paste of the paste spread thinly on the print mask 32 is faded, so that uniform printing cannot be performed.

  Note that the lower limit of the viscosity of the paste is about 30 Pa · s from the viewpoint of obtaining a desired pattern dimension by the screen printing method, in particular, obtaining a desired fine line width (not exceeding a desired width).

  As described above, the screen printing machine according to the present invention is useful for continuous printing with good print quality without causing printing failure due to insufficient paste amount.

  DESCRIPTION OF SYMBOLS 1 Solar cell, 2 Semiconductor substrate (p-type silicon substrate), 2a Minute unevenness, 3 n-type impurity diffusion layer, 3a 1n-type impurity diffusion layer, 3b 2n-type impurity diffusion layer, 4 Antireflection film, 5 Surface silver Grid electrode, 5a silver paste, 6 front silver bus electrode, 7 back aluminum electrode, 7a aluminum paste, 8 back silver electrode, 9 p + layer (BSF (Back Surface Field)), 11 semiconductor substrate, 12 light receiving surface side electrode, 13 Back side electrode, 21 Dopant-containing paste, 31 Printing stage, 32 Printing mask, 33 Printing mask frame, 34 Squeegee, 35 Scraper, 35a Bending part, 36 Bank member, 37 Rubber plate, 38 Groove part, 40 Guide wall, 41 Notch Part, 42 Notch part, Y1 coat direction, Y2 printing direction.

Claims (6)

A screen printing machine that prints a paste coated on a printing area of a printing mask on a printing surface of a printing material arranged at a lower part of the printing area through an opening pattern provided in the printing area,
A scraper that coats the printing region with the paste supplied to the upper surface of the printing mask by sliding on the upper surface of the printing mask in a state of being separated from the upper surface of the printing mask;
By sliding in the direction opposite to the sliding direction of the scraper while contacting the upper surface of the printing mask on the printing area coated with the paste, the paste is applied to the printing surface via the opening pattern. Squeegee to print on,
The upper surface of the printing mask and at least the side surface on the printing region side are closely attached to the outer peripheral side of the sliding region of the scraper on the upper surface of the printing mask, and the paste protruding from the sliding region of the scraper is provided. A bank member that rebounds to the sliding area side of the scraper,
The bank member has an inclined surface on the upper surface that becomes lower from the downstream side toward the upstream side in the sliding direction of the scraper,
When the scraper and the squeegee slide, the paste that protrudes from the sliding area of the scraper and moves to the inclined surface flows to the upstream side due to the inclination of the inclined surface, and then flows to the upper surface of the printing mask and moves to the upper surface. Return to the sliding area of the scraper,
A screen printer. A tip portion in the width direction of the scraper is a bent portion bent downstream in the sliding direction of the scraper,
The bent portion protrudes from the sliding region of the scraper and moves to the bank member side from the printing region in the sliding region of the scraper by the bank member, and causes the printing region to move when the scraper slides. Raked into the
The screen printer according to claim 1. An outer peripheral edge on the printing region side of the inclined surface of the bank member has a guide wall extending in the inclination direction of the inclined surface along the side wall on the printing region side and protruding upward from the inclined surface. ,
The paste moved to the inclined surface moves the inclined surface from the downstream side to the upstream side along the guide wall;
The screen printer according to claim 1 or 2. The viscosity of the paste is 80 Pa · s or less,
The screen printer according to any one of claims 1 to 3. The upstream side of the inclined surface has a slope that decreases from the outer peripheral side of the printing mask toward the printing region;
The screen printing machine according to any one of claims 1 to 4. Having a groove for guiding the paste extending toward the upstream side from the downstream side to the inclined surface,
The screen printer according to any one of claims 1 to 5.

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