PRINTING STENCIL AND PRINTING DEVICES FOR FORMING CONDUCTOR PATHS ON A SUBSTRATE AND METHOD FOR PRODUCING A METAL CONTACT STRUCTURE OF A PHOTOVOLTAIC CELL

Abstract

A printing stencil (1) for forming conductor tracks on a substrate. The printing stencil (1) has a plurality of cutouts in the form of printing gaps (4) for forming the conductor tracks. Each printing gap (4) of the plurality of printing gaps (4) has at least one print definition region (3) adjacent to the printing side and at least one printing medium supply region (2) adjacent to the squeegee side, the volume of the print definition region (3) being smaller than the volume of the printing medium supply region. Moreover, a printing device for forming conductor tracks on a substrate and a method for producing a metallic contact structure of a photovoltaic solar cell are also provided.

Claims

1. A printing stencil (1) for forming conductor tracks on a substrate, the printing stencil (1) comprising: a planar stencil body having a plurality of cutouts in that form printing gaps (4) for forming the conductor tracks on the substrate, the planar material having a substrate side (S) and a squeegee side (R) opposite the substrate side (S), and each printing gap (4) of the plurality of printing gaps (4) has at least one print definition region (3) adjacent to the printing side and at least one printing medium supply region (2) adjacent to the squeegee side (R), a volume of the print definition region (3) being smaller than a volume of the printing medium supply region (2), the printing medium supply region (2) has an increasing gap width, in a direction of the squeegee side (R), and at least one of a) walls of the print definition region (3) form a first opening angle () which is smaller than a second opening angle () formed by walls of the printing medium supply region (2), or b) the print definition region (3) has an increasing gap width, in a direction of the substrate side (S).

2. The printing stencil (1) as claimed in claim 1, wherein the walls of the print definition region (3) form the opening angle () that is smaller than the second opening angle formed by the walls of the printing medium supply region (2) by 10 or more.

3. The printing stencil (1) as claimed in claim 1, wherein the printing stencil has a thickness of 50 m.

4. The printing stencil (1) as claimed in claim 1, wherein the print definition region (3) has a thickness of less than 250 m.

5. The printing stencil (1) as claimed in claim 1, wherein the stencil body is formed of one of the materials of glass, stainless steel, or silicon.

6. The printing stencil (1) as claimed claim 1, wherein the width of each said printing gap (4) of the plurality of printing gaps (4) is less than 50 m, at an end of the print definition region (3) nearest to the squeegee side (R).

7. The printing stencil (1) as claimed in claim 1, wherein the width of each said printing gap (4) of the plurality of printing gaps (4) is less than 50 m, at an end of the print definition region (3) nearest to the substrate side (S).

8. The printing stencil (1) as claimed in claim 1, wherein the width of each said printing gap (4) of the plurality of printing gaps (4) is greater than 15 m, an end of the printing medium supply region (2) nearest to the squeegee side (R).

9. The printing stencil (1) as claimed in claim 1, wherein the printing medium supply region (2) terminates directly at the squeegee side (R), and the print definition region (3) terminates directly at the substrate side (S).

10. A printing plate, having the printing stencil (1) as claimed in claim 1, the printing stencil being arranged in a frame.

11. The printing plate as claimed in claim 10, wherein no carrier structures are formed on openings of the printing gaps (4).

12. A printing device for forming conductor tracks on a substrate, comprising the printing stencil (1) as claimed in claim 1 and at least one squeegee, the screen printing device being designed to apply printing medium through the screen printing plate onto the substrate via the squeegee.

13. A method for producing a metallic contact structure of a photovoltaic solar cell, the method comprising the following method steps: applying printing medium to a squeegee side (R) of a printing stencil (1), printing the printing medium through printing gaps (4) in the printing stencil (1) via at least one squeegee in order to apply a printing medium structure to a solar cell substrate on a substrate side (S) of the printing stencil opposite the squeegee side (R), the printing stencil (1) is formed as a planar printing stencil (1), having the substrate side (S) and the squeegee side (R) opposite the substrate side (S), and each printing gap (4) of the plurality of printing gaps (4) has at least one print definition region (3) adjacent to the printing side and at least one printing medium supply region (2) adjacent to the squeegee side (R), a volume of the print definition region (3) being smaller than a volume of the printing medium supply region (2), the printing medium supply region (2) has an increasing gap width, in a direction of the squeegee side (R), and at least one of a) walls of the print definition region (3) form a first opening angle () which is smaller than a second opening angle () formed by walls of the printing medium supply region (2) or b) the print definition region (3) has an increasing gap width, in a direction of the substrate side (S).

14. The method of claim 13, further comprising forming metallic conductor tracks of a photovoltaic solar cell.

15. The method of claim 14, wherein the metallic conductor tracks are formed on a front side of the photovoltaic solar cell facing the incident light

16. The printing stencil (1) as claimed in claim 9, wherein the printing medium supply region (2) and print definition region (3) are adjacent to one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Further preferred features and embodiments are explained below on the basis of exemplary embodiments and figures. In this context,

[0058] FIGS. 1 and 2 each show an exemplary embodiment of a printing gap of the printing stencil according to the invention.

[0059] FIG. 3 shows an exemplary embodiment of a printing stencil according to the invention.

[0060] FIG. 4 shows an exemplary embodiment of a printing device according to the invention.

DETAILED DESCRIPTION

[0061] The figures show schematic illustrations which are not true to scale. Identical reference signs in the figures designate identical or identically acting elements.

[0062] The exemplary embodiment of a printing stencil according to the invention shown in FIG. 1 is shown in a cross-sectional view, with a detail of the printing stencil with a printing gap being depicted. The printing stencil continues to the right and left in the same way. Overall, the printing stencil in the present case has 19 printing gaps which are arranged in parallel and have the same geometry.

[0063] On a squeegee side R, located at the top in the figures, the planar printing stencil 1 has an opening with an opening angle . On a substrate side S, located at the bottom in the figures, the printing stencil 1 has an opening with an opening angle . The squeegee-side opening angle is greater than the substrate-side opening angle . Both opening angles are oriented in the same sense.

[0064] In this exemplary embodiment, a printing medium supply region 2 is formed by way of a volume that is delimited by the squeegee-side printing stencil top side and the opening flanks of the channel walls of the opening defined by the opening angle .

[0065] In this exemplary embodiment, a print definition region 3 is formed by way of a volume that is delimited by the substrate-side printing stencil bottom side S and the opening flanks of the printing gap opening defined by the opening angle .

[0066] The printing medium supply region 2 thus terminates directly at the squeegee side. By contrast, the print definition region 3 terminates directly at the substrate side.

[0067] In this arrangement, the printing medium supply region and the print definition region are adjacent to one another. In this exemplary embodiment, the printing medium supply region height H2 is chosen to be higher than the print definition region height H3. Furthermore, the volume of the printing medium supply region 2 is greater than the volume of the print definition region 3; this promotes the ability to feed sufficient amounts of printing medium.

[0068] The exemplary embodiment of a printing stencil according to the invention shown in FIG. 2 is shown in a cross-sectional view, with a detail of the printing stencil with a printing gap being depicted. The printing stencil continues to the right and left in the same way. Overall, the printing stencil in the present case has 19 printing gaps which are arranged in parallel and have the same geometry.

[0069] On a squeegee side R, located at the top in the figures, the planar printing stencil 1 has an opening with an opening angle . On a substrate side S, located at the bottom in the figures, the printing stencil 1 has an opening with an opening angle . The squeegee-side opening angle is greater than the substrate-side opening angle . The two opening angles are oriented in opposite senses. As a result, the two regions form an hourglass shape.

[0070] In this exemplary embodiment, a printing medium supply region 2 is formed by way of a volume that is delimited by the squeegee-side printing stencil top side and the opening flanks of the channel walls of the opening defined by the opening angle .

[0071] In this exemplary embodiment, a print definition region 3 is formed by way of a volume that is delimited by the substrate-side printing stencil bottom side S and the opening flanks of the printing gap opening defined by the opening angle .

[0072] The printing medium supply region 2 thus terminates directly at the squeegee side. By contrast, the print definition region 3 terminates directly at the substrate side.

[0073] In this arrangement, the printing medium supply region 2 and the print definition region 3 are adjacent to one another. In this exemplary embodiment, the printing medium supply region height H2 is chosen to be higher than the print definition region height H3. Furthermore, the volume of the printing medium supply region 2 is greater than the volume of the print definition region 3; this promotes the ability to feed sufficient amounts of printing medium.

[0074] FIG. 3 shows an exemplary embodiment of a printing stencil 1 according to the invention in a plan view. The printing stencil 1 has a square embodiment, and the present printing stencil has 19 printing gaps which are arranged in parallel and have the same geometry. In this embodiment, the printing gaps 4 are arranged parallel to one another and parallel to an edge of the printing stencil 2. As a result of the printing gaps 4, it is possible to create straight-line structures of printing medium on the substrate. These structures represent metallic contacting elements.

[0075] The plan view shown in FIG. 3 also corresponds to the plan view of the exemplary embodiments shown in FIGS. 1 and 2.

[0076] FIG. 4 schematically illustrates an exemplary embodiment of a printing device according to the invention. The printing device comprises a printing plate formed by a printing stencil 1 according to the exemplary embodiment shown in Figure 1 and a frame 5. The printing stencil 1 is arranged in the frame 5. The printing plate with the printing stencil 1 and frame 5 thus represents an exemplary embodiment of a printing plate according to the invention which has no carrier structures, in particular no screen printing fabric, at the openings of the printing gaps 4.

[0077] Above the printing plate, a squeegee 6 is arranged on a movement unit 7. The movement unit 7 and the frame 5 are arranged on a mount (not depicted here) of the printing device, which also has a support for a substrate 8. The substrate 8 represents a precursor of a silicon solar cell, to which metallic contacting fingers 10 should be applied. A printing medium supply unit (likewise not depicted here) of the printing device is used to apply a metal particle-containing printing paste 9 to the squeegee side of the printing stencil 1 located at the top.

[0078] The movement unit 7 is used to move the squeegee 6 over the printing stencil 1 and the printing paste 9 is forced onto the substrate 8 through the printing gaps 4 of the printing stencil 1 as a result, and so printing paste in the form of thin, straight-line contacting fingers 10 arranged in parallel is applied to the substrate 8.

[0079] FIG. 4 shows a schematic illustration. In a real embodiment, the printing stencil 1 in the region of the squeegee 6 typically has a slight bend in the direction of the substrate 8.

LIST OF REFERENCE SIGNS

[0080] 1 Printing stencil [0081] 2 Printing medium supply region [0082] 3 Print definition region [0083] 4 Printing gap [0084] 5 Frame [0085] 6 Squeegee [0086] 7 Movement unit [0087] 8 Substrate [0088] 9 Printing paste [0089] 10 Contact finger [0090] R Squeegee side [0091] S Substrate side [0092] , Opening angle