Manufacturing method of screen transfer design, screen and printing system

Abstract

The invention discloses a manufacturing method of a screen transfer printing design and a screen and a printing system thereof, and belongs to the technical field of solar cells, and the manufacturing method comprises the following steps: preparing a screen of an upper wear-resistant slipping layer, a metal sealing layer, a slotting layer and a lower wear-resistant slipping layer which are sequentially stacked from top to bottom, the groove area is filled with slurry from the lower portion through a nozzle, and meanwhile the upper surface of the screen printing plate reciprocates along the lower edge through a scraper; the lower surface of the screen printing plate is subjected to scraping treatment through a secondary scraping plate, and slurry residues in a non-groove area are removed; applying pressure to the upper surface of the screen printing plate by using a scraper to extrude, so that the slurry is separated from the groove and transferred to the surface of the substrate; and after plate separation, transferring the slurry to a base material, and sintering and curing. The multi-layer composite screen design is adopted, the thickened metal supporting layer remarkably enhances the mechanical strength and the abrasion resistance of the screen, deformation in the long-term printing process is effectively reduced, the service life of the screen is prolonged, and the production cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cell manufacturing, and particularly relates to a manufacturing method of a screen transfer design, a screen and a printing system thereof. Background Art

[0002] Screen printing is an important process in the production of solar cells. Photovoltaic solar wafers are fabricated using screen printing technology, that is, a screen is placed on the surface of the wafer, and a squeegee is used to coat the paste on the screen, so that the paste penetrates through the screen holes and is imprinted on the wafer to form a circuit or electrode. Its printing quality directly affects various performances of the solar wafer. Screen printing technology is the key process to achieve precise pattern transfer.

[0003] In the prior art, conventional screens mainly adopt two structural forms: a knotless woven screen and a full-opening steel mesh screen. The knotless woven screen is woven by metal wires perpendicular to each other, and the weaving knots are removed in the area to be printed to form paste-permeable holes; the full-opening steel mesh screen is directly provided with a printing window on the whole metal plate. Both of these screens rely on the permeable film printing principle that the paste penetrates the screen from top to bottom. Its working principle includes three key steps: the "rotation" paste-laying stage: the squeegee reciprocates on the screen surface to lay the paste; the filling and extrusion stage: the squeegee applies pressure to the screen to make the paste penetrate the holes and form a printing pattern on the wafer; the oven sintering stage: the paste is cured at high temperature to form a metal grid line.

[0004] However, both of the above two types of screens require the paste to penetrate the entire screen thickness under the action of the squeegee. To ensure the penetrability of the paste, the total screen thickness is strictly limited, resulting in insufficient structural strength of the screen. After long-term use, the screen tension becomes smaller, the openings for the paste to penetrate the screen become larger, the screen printing pattern will expand outward, and the single printing pattern will also gradually widen, increasing the optical shading area, and the screen life and stability are insufficient.

[0005] In view of this, the inventor of the present invention conducted in-depth research on this need, and thus this case was born. Summary of the Invention

[0006] To solve the problems in the prior art that the screen printing thickness limitation leads to insufficient structural strength of the screen, the screen tension becomes smaller after long-term use, the screen printing pattern expands outward, the optical shading area increases, and the screen life and stability are insufficient, the present invention provides a manufacturing method of a screen transfer design, a screen and a printing system thereof, specifically as follows:

[0007] A manufacturing method of a screen transfer design includes the following steps:

[0008] Step 1: Prepare a stencil with a total thickness of 15 - 200 μm. The stencil includes an upper wear-resistant and slip-increasing layer, a metal sealing layer, a grooving layer, and a lower wear-resistant and slip-increasing layer stacked in sequence from top to bottom. A number of grooves are equidistantly arranged on the grooving layer. The lower wear-resistant and slip-increasing layer covers the end face of the non-grooved area of the grooving layer. The inner surface of the grooves is treated by sandblasting or laser to form a number of circular protrusions.

[0009] Step 2: Fill the groove area with the slurry from below through a nozzle. The nozzle pressure is 50 - 200 N / cm 2 , and at the same time, use a squeegee to reciprocate along the lower edge on the upper surface of the stencil under a pressure of 20 - 70 N / cm 2 .

[0010] Step 3: Scrape and level the lower surface of the stencil with a secondary squeegee to remove the slurry residue in the non-grooved area.

[0011] Step 4: Apply a pressure of 20 - 100 N / cm 2 to the upper surface of the stencil with a squeegee to extrude the slurry out of the grooves and transfer it to the surface of the substrate.

[0012] Step 5: After separating from the stencil, transfer the slurry to the substrate and sinter and cure it.

[0013] Further, the groove width is 3 - 15 μm and the groove depth is 3 - 15 μm.

[0014] Further, the groove cross-sectional shape of the groove is selected from at least one of trapezoid, circle, or rectangle.

[0015] Further, the protrusion height is 0.05 - 0.2 μm, the bottom diameter is 0.05 - 0.5 μm, and the number is 10 - 50 per mm 2 .

[0016] Further, the thickness of the upper wear-resistant and slip-increasing layer is 1 - 15 μm, the thickness of the metal sealing layer is 10 - 150 μm, the thickness of the grooving layer is 5 - 20 μm, and the thickness of the lower wear-resistant and slip-increasing layer is 1 - 15 μm.

[0017] Further, the slurry viscosity is 5000 - 20000 cps, the substrate is a silicon wafer for solar cells, and the printing grid line density is 170 - 500 lines per wafer.

[0018] Further, a metal transition layer with a thickness of 0.5 - 3 μm is provided between the metal sealing layer and the grooving layer, and the metal sealing layer and the grooving layer are integrally formed by electroforming.

[0019] Further, the materials of the upper wear-resistant and slip-increasing layer and the lower wear-resistant and slip-increasing layer are selected from any one of PI films or resins, and the material of the metal sealing layer is selected from any one of stainless steel, nickel alloys or copper alloys.

[0020] The present application also provides a stencil, which is obtained by using the manufacturing method of the stencil transfer design as described above. The total thickness of the stencil is 15 - 200 μm, and it includes an upper wear-resistant and slip-increasing layer, a metal sealing layer, a grooving layer, and a lower wear-resistant and slip-increasing layer that are stacked in sequence from top to bottom. A number of grooves are equidistantly arranged on the grooving layer, and the lower wear-resistant and slip-increasing layer covers the non-grooved area of the grooving layer. The width of the groove is 3 - 15 μm, and the depth is 3 - 15 μm. The inner surface of the groove is treated by sandblasting or laser to form a number of circular protrusions, and a 0.5 - 3 μm metal transition layer is provided between the metal sealing layer and the grooving layer.

[0021] The present application also provides a printing system for manufacturing the stencil as described above, including a nozzle, an upper squeegee, and a lower squeegee. The filling pressure of the nozzle is 50 - 200 N / cm 2 , the demolding pressure of the upper squeegee is 20 - 100 N / cm 2 , the scraping edge pressure of the lower squeegee is 20 - 70 N / cm 2 , and the working distance between the upper squeegee and the nozzle is 0.5 - 2 mm;

[0022] The printing system further includes a closed-loop control system for controlling the nozzle pressure and the working distance between the upper squeegee and the nozzle. The closed-loop control system is electrically connected to the nozzle, the upper squeegee, and the lower squeegee respectively. The curvature radii of the working surfaces of the upper squeegee and the lower squeegee are adapted to the total thickness of the stencil.

[0023] Beneficial effects:

[0024] The beneficial effects produced by adopting the technical solution of the present invention are as follows:

[0025] (1) By adopting a multi-layer composite stencil design, the total thickness of the stencil is extended to the range of 15 - 200 μm. Compared with the traditional stencil with a thickness of 15 - 25 μm, the thickness increase amplitude exceeds 8 times. The thickened metal support layer significantly enhances the mechanical strength and wear resistance of the stencil, effectively reduces the deformation during the long-term printing process, greatly extends the service life of the stencil, and reduces the production cost significantly.

[0026] (2) Change the dependence limitation of traditional membrane-penetrating printing on the screen thickness. Through a new printing mode of filling the paste below and squeezing it with the squeegee above, the plasticizing height of the paste is completely controlled by the squeegee pressure. Eliminate the restriction of the screen thickness on the printing height. While maintaining an ultra-narrow line width of 3 - 15 μm, a printing height equal to or even higher than the line width can be achieved, ensuring precise control of the cross-sectional morphology of the grid lines.

[0027] (3) The groove structure design combined with the optimization of surface roughness significantly enhances the adaptability of the screen to high-viscosity paste. It can not only achieve the minimum line width, but also improve the current collection efficiency under the same light-shielding area by increasing the grid line density per unit area.

[0028] (4) Through the precise ratio design of the groove depth and width, while maintaining the fineness of the grid lines, the printing height is maximized. This high aspect ratio structure can effectively reduce the grid line resistance. Using the present invention in combination with a special nozzle-squeegee combination device significantly improves the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is a schematic structural diagram of a screen of the present invention;

[0031] In the figure, 1, upper wear-resistant and slip-increasing layer; 2, metal sealing layer; 3, grooved layer; 4, lower wear-resistant and slip-increasing layer; 5, groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0033] In this embodiment, a multi-layer composite screen printing plate design is adopted, and the total thickness of the screen printing plate is extended by more than 8 times compared with the traditional screen printing plate thickness. The thickened metal support layer significantly enhances the mechanical strength and wear resistance of the screen printing plate, effectively resists deformation loss during long-term printing, extends the service life of the screen printing plate to 3-5 times that of the traditional screen printing plate, and greatly reduces the production cost. The specific implementation methods are as follows:

[0034] Referring to Figure 1 as shown, a manufacturing method of a screen printing plate transfer design includes the following steps:

[0035] The first step: Prepare a screen printing plate with a total thickness of 15-200 μm. The screen printing plate includes an upper wear-resistant and lubricating layer 1, a metal sealing layer 2, a grooved layer 3, and a lower wear-resistant and lubricating layer 4 that are stacked in sequence from top to bottom. A plurality of grooves 5 are equidistantly formed on the grooved layer 3. The lower wear-resistant and lubricating layer 4 covers the end face of the non-grooved area of the grooved layer 3. The inner surface of the groove 5 is treated by sandblasting or laser to form a plurality of circular protrusions;

[0036] The second step: Fill the groove 5 area with slurry from below through a nozzle. The nozzle pressure is 50-200 N / cm 2 , and at the same time, use a squeegee to reciprocate on the upper surface of the screen printing plate along the lower edge under a pressure of 20-70 N / cm 2 ;

[0037] The third step: Use a secondary squeegee to level the lower surface of the screen printing plate to remove the slurry residue in the non-groove 5 area;

[0038] The fourth step: Apply a pressure of 20-100 N / cm 2 to the upper surface of the screen printing plate with a squeegee to extrude the slurry out of the groove 5 and transfer it to the surface of the substrate;

[0039] The fifth step: After separating from the plate, transfer the slurry to the substrate and sinter and cure it.

[0040] As a preferred embodiment, the groove width of the groove 5 is 3-15 μm, and the groove depth is 3-15 μm.

[0041] As a preferred embodiment, the groove cross-section of the groove 5 is selected from at least one of trapezoid, circle, or rectangle.

[0042] As a preferred embodiment, the height of the protrusion is 0.05-0.2 μm, the bottom diameter is 0.05-0.5 μm, and the number is 10-50 per mm 2 .

[0043] As a preferred embodiment, the thickness of the upper wear-resistant and lubricating layer 1 is 1-15 μm, the thickness of the metal sealing layer 2 is 10-150 μm, the thickness of the grooved layer 3 is 5-20 μm, and the thickness of the lower wear-resistant and lubricating layer 4 is 1-15 μm.

[0044] As a preferred embodiment, the viscosity of the slurry is 5000-20000 cps, the substrate is a silicon wafer for a solar cell, and the printed grid line density is 100-500 lines per wafer.

[0045] As a preferred embodiment, a metal transition layer with a thickness of 0.5-3 μm is provided between the metal sealing layer 2 and the grooved layer 3, and the metal sealing layer 2 and the grooved layer 3 are integrally formed by electroforming.

[0046] As a preferred embodiment, the materials of the upper wear-resistant and lubricating layer 1 and the lower wear-resistant and lubricating layer 4 are selected from any one of PI films or resins, and the material of the metal sealing layer 2 is selected from any one of stainless steel, nickel alloy or copper alloy.

[0047] This embodiment also provides a stencil, which is obtained by using the manufacturing method of the stencil transfer printing design as described above. The total thickness of the stencil is 15-200 μm, and it includes an upper wear-resistant and lubricating layer 1, a metal sealing layer 2, a grooved layer 3, and a lower wear-resistant and lubricating layer 4 that are stacked in sequence from top to bottom. A number of grooves 5 are equidistantly arranged on the grooved layer 3, and the lower wear-resistant and lubricating layer 4 covers the non-grooved area of the grooved layer 3. The width of the groove 5 is 3-15 μm, and the depth is 3-15 μm. The inner surface of the groove 5 is formed with a number of circular protrusions by sandblasting or laser treatment. A metal transition layer with a thickness of 0.5-3 μm is provided between the metal sealing layer 2 and the grooved layer 3.

[0048] This embodiment also provides a printing system for manufacturing the stencil as described above, including a nozzle, an upper squeegee, and a lower squeegee. The filling pressure of the nozzle is 50-200 N / cm 2 , the demolding pressure of the upper squeegee is 20-100 N / cm 2 , the scraping edge pressure of the lower squeegee is 20-70 N / cm 2 , and the working distance between the upper squeegee and the nozzle is 0.5-2 mm;

[0049] The printing system further includes a closed-loop control system for controlling the nozzle pressure and the working distance between the upper squeegee and the nozzle. The closed-loop control system is electrically connected to the nozzle, the upper squeegee, and the lower squeegee respectively. The curvature radii of the working surfaces of the upper squeegee and the lower squeegee are adapted to the total thickness of the stencil.

[0050] Example 1

[0051] In this embodiment, a manufacturing method for screen printing transfer design is provided, including the following steps:

[0052] The first step: Prepare a screen with a total thickness of 15 μm, which includes the following layers stacked from top to bottom:

[0053] The first layer, an upper wear-resistant and lubricating layer 1 with a thickness of 1 μm and composed of polyimide PI;

[0054] The second layer, a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0055] The third layer, a grooved layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 with a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is laser-treated to form protrusions with a height of 0.1 μm, and the density of the protrusions is 20 per mm 2 ;

[0056] The fourth layer, a lower wear-resistant and lubricating layer 4 with a thickness of 1 μm and composed of a PI film.

[0057] The second step: Use silver paste with a viscosity of 8000 cps, and fill the groove 5 from below the screen through a nozzle with a pressure of 50 N / cm 2 At the same time, the upper squeegee reciprocates and levels with a pressure of 20 N / cm 2 The distance between the squeegee and the nozzle is 0.5 mm.

[0058] The third step: Level the lower surface of the screen by using a secondary squeegee to remove the residue on the lower surface of the screen.

[0059] The fourth step: Apply a pressure of 30 N / cm 2 to the upper surface of the screen by using a squeegee to extrude, so that the slurry detaches from the groove 5 and is transferred to the surface of the substrate, and the transfer rate in the groove is 95%.

[0060] The fifth step: After separating from the plate, sintering is carried out to form a grid line density of 170 lines per sheet, and the line width accuracy is ±0.3 μm.

[0061] Example 2

[0062] In this embodiment, a manufacturing method for screen printing transfer design is provided, including the following steps:

[0063] The first step: Prepare a screen with a total thickness of 50 μm, which includes the following layers stacked from top to bottom:

[0064] The first layer, an upper wear-resistant and lubricating layer 1 with a thickness of 5 μm and composed of PI;

[0065] The second layer, a stainless steel metal sealing layer 2 with a thickness of 30 μm;

[0066] The third layer is a grooved layer 3 formed by electroforming in one piece, with a thickness of 10 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 with a width of 11 μm and a depth of 10 μm. The inner surface of the groove 5 is laser-treated to form a 0.1-μm protrusion, and the density of the protrusions is 30 per mm 2 ;

[0067] The fourth layer is a lower wear-resistant and slip-increasing layer 4 with a thickness of 5 μm and composed of a PI film.

[0068] The second step: Use silver paste with a viscosity of 12,000 cps and fill the groove 5 from below the stencil through a nozzle with a pressure of 120 N / cm 2 At the same time, the upper squeegee reciprocates to scrape flat with a pressure of 45 N / cm 2 The distance between the squeegee and the nozzle is 1 mm.

[0069] The third step: Scrape and level the lower surface of the stencil by using a secondary squeegee to remove the residue on the lower surface of the stencil.

[0070] The fourth step: Apply a pressure of 80 N / cm 2 to the upper surface of the stencil by using a squeegee to extrude, so that the slurry detaches from the groove 5 and is transferred to the surface of the substrate.

[0071] The fifth step: After leaving the plate, sintering is carried out to form a grid line density of 200 per sheet, and the line width accuracy is ±0.2 μm.

[0072] Example 3

[0073] A manufacturing method for a stencil transfer design, comprising the following steps:

[0074] The first step: Manufacture a stencil with a total thickness of 80 μm. The stencil includes, from top to bottom, the following layers stacked in sequence:

[0075] The first layer is an upper wear-resistant and slip-increasing layer 1 with a thickness of 8 μm and composed of a resin layer;

[0076] The second layer is a nickel alloy metal sealing layer 2 with a thickness of 60 μm;

[0077] The third layer is a grooved layer 3 formed by electroforming in one piece, with a thickness of 7 μm, provided with a groove 5 with a rectangular cross-section width of 9.5 μm and a depth of 9.5 μm. A 2-μm copper transition layer is provided between the metal sealing layer 2 and the grooved layer 3. The inner surface of the groove 5 is sandblasted to form a 0.15-μm protrusion, and the density of the protrusions is 30 per mm 2 ;

[0078] The fourth layer is a lower wear-resistant and slip-increasing layer 4 with a thickness of 5 μm and composed of a PI film.

[0079] The second step: Use silver paste with a viscosity of 18,000 cps and fill the groove 5 from below the stencil through a nozzle with a pressure of 180 N / cm 2The nozzle fills the groove 5 from below the stencil, while the upper squeegee reciprocates and levels at a pressure of 70 N / cm 2 and the working distance between the squeegee and the nozzle is 1 mm.

[0080] Step 3: Level the lower surface of the stencil by using a secondary squeegee to remove the slurry residue in the area other than the groove 5. The radius of curvature of the secondary squeegee matches the thickness of the stencil, and the scraping rate reaches 99.5%.

[0081] Step 4: Apply a pressure of 100 N / cm 2 to the upper surface of the stencil by using a squeegee to extrude the slurry so that the slurry detaches from the groove 5 and is transferred to the surface of the substrate, and the transfer rate of the slurry in the groove is 98.7%.

[0082] Step 5: Sinter at a low temperature to form 250 microcircuits per sheet, and the line width accuracy is ±0.15 μm.

[0083] Example 4

[0084] A manufacturing method of a stencil transfer design includes the following steps:

[0085] Step 1: Manufacture a stencil with a total thickness of 120 μm, which includes, from top to bottom, the following layers stacked in sequence:

[0086] The first layer, an upper wear-resistant and slip-increasing layer 1 with a thickness of 10 μm and composed of a resin layer;

[0087] The second layer, a nickel alloy metal sealing layer 2 with a thickness of 80 μm;

[0088] The third layer, a grooved layer 3 formed by electroforming in one piece, with a thickness of 20 μm. The grooved layer 3 is provided with a groove 5 having a rectangular cross-section with a width of 8.5 μm and a depth of μm. A 2-μm copper transition layer is provided between the metal sealing layer 2 and the grooved layer 3. The inner surface of the groove 5 is treated by laser to form a 0.2-μm protrusion, and the density of the protrusions is 40 per mm 2 ;

[0089] The fourth layer, a lower wear-resistant and slip-increasing layer 4 composed of a PI film with a thickness of 10 μm.

[0090] Step 2: Configure a multi-stage filtering device to process 8000 cps nano-silver paste with a particle size ≤ 0.7 μm. The nozzle with a pressure of 200 N / cm 2 fills the groove 5 from below the stencil, while the upper squeegee reciprocates and levels at a pressure of 100 N / cm 2 and the distance is 2 mm.

[0091] Step 3: Level the lower surface of the stencil by using a secondary squeegee to remove the slurry residue in the area other than the groove 5. After transfer to a glass substrate, the detection shows that the slurry residue in the groove 5 is < 0.3%, and the line width consistency reaches ±0.15 μm.

[0092] Step 4: Use a squeegee to apply a pressure of 100 N / cm 2 to extrude the paste from the groove 5 and transfer it to the surface of the substrate, with a paste transfer rate of 98.7% in the groove.

[0093] Step 5: Sinter at a low temperature to form 300 microcircuits per chip, with a line width accuracy of ±0.3 μm.

[0094] Example 5

[0095] This example prepares a manufacturing method for a stencil transfer design, including the following steps:

[0096] Step 1: Prepare a stencil with a total thickness of 150 μm, which includes the following layers stacked from top to bottom:

[0097] The first layer, an upper wear-resistant and lubricating layer 1 with a thickness of 15 μm and composed of PI;

[0098] The second layer, a stainless steel metal sealing layer 2 with a thickness of 125 μm;

[0099] The third layer, a grooved layer 3 formed by electroforming in one piece, with a thickness of 20 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 with an upper width of 7.5 μm and a depth of 9 μm. The inner surface of the groove 5 is laser-treated to form protrusions with a height of 0.2 μm and a density of 40 protrusions / mm 2 ;

[0100] The fourth layer, a lower wear-resistant and lubricating layer 4 with a thickness of 10 μm and composed of a PI film.

[0101] Step 2: Use a silver paste with a viscosity of 20000 cps and fill the groove 5 from below the stencil through a nozzle with a pressure of 200 N / cm 2 , while the upper squeegee reciprocates to scrape flat with a pressure of 70 N / cm 2 , and the distance between the squeegee and the nozzle is 2 mm.

[0102] Step 3: Scrape and level the lower surface of the stencil by using a secondary squeegee to remove the residue on the lower surface of the stencil.

[0103] Step 4: Use a squeegee to apply a pressure of 100 N / cm 2 to extrude the paste from the groove 5 and transfer it to the surface of the substrate.

[0104] Step 5: After peeling off the stencil, sinter to form a grid line density of 400 lines per chip, with a line width accuracy of ±0.1 μm.

[0105] Example 6

[0106] This example prepares a manufacturing method for a stencil transfer design, including the following steps:

[0107] Step 1: Prepare a stencil with a total thickness of 200 μm, which includes the following layers stacked from top to bottom:

[0108] The first layer is an upper wear-resistant and lubricating layer 1 with a thickness of 15 μm and composed of PI;

[0109] The second layer is a stainless-steel metal sealing layer 2 with a thickness of 150 μm;

[0110] The third layer is a slotted layer 3 formed by electroforming in one piece, with a thickness of 20 μm. The slotted layer 3 is provided with a rectangular cross-section groove 5 with an upper width of 6 μm and a depth of 8 μm. The inner surface of the groove 5 is laser-treated to form protrusions with a height of 0.2 μm, and the density of the protrusions is 50 per mm 2 ;

[0111] The fourth layer is a lower wear-resistant and lubricating layer 4 with a thickness of 15 μm and composed of a PI film.

[0112] Step 2: Use silver paste with a viscosity of 20000 cps to fill the groove 5 from below the stencil through a nozzle with a pressure of 200 N / cm 2 Meanwhile, the upper squeegee reciprocates to scrape flat with a pressure of 70 N / cm 2 The distance between the squeegee and the nozzle is 2 mm.

[0113] Step 3: Scrape and level the lower surface of the stencil through the use of a secondary squeegee to remove the residue on the lower surface of the stencil.

[0114] Step 4: Apply a pressure of 100 N / cm 2 to the upper surface of the stencil with a squeegee for extrusion, so that the slurry detaches from the groove 5 and is transferred to the surface of the substrate.

[0115] Step 5: After leaving the plate, sintering is carried out to form a grid line density of 500 per sheet, and the line width accuracy is ±0.1 μm.

[0116] Next, the solar cell wafers produced by the stencils obtained in the above 1-6 groups of examples (taking a silicon wafer with a size of 183.75 cm × 182.2 cm as an example, and the basic area is 33471 mm 2 , removing 4 chamfers) are subjected to performance tests, and the results are as follows:

[0117] Table 1 Performance test results of solar cell wafers produced by the stencils obtained in each group of examples

[0118]

[0119] Comparative Example 1

[0120] In this example, a manufacturing method for stencil transfer design is prepared, including the following steps:

[0121] Step 1: Prepare a stencil with a total thickness of 15 μm. The stencil includes, from top to bottom and stacked in sequence:

[0122] The first layer, an upper wear-resistant and lubricating layer 1 with a thickness of 1 μm and composed of polyimide PI;

[0123] The second layer, a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0124] The third layer, a grooved layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 with a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is laser-treated to form protrusions with a height of 0.1 μm, and the density of the protrusions is 20 per mm 2 ;

[0125] The fourth layer, a lower wear-resistant and lubricating layer 4 with a thickness of 1 μm and composed of a PI film.

[0126] Step 2: Use a silver paste with a viscosity of 8000 cps, and fill the groove 5 from below the stencil through a nozzle with a pressure of 50 N / cm 2 Meanwhile, the upper squeegee reciprocates to scrape and level at a pressure of 20 N / cm 2 The distance between the squeegee and the nozzle is 0.5 mm.

[0127] Step 3: Scrape and level the lower surface of the stencil by using a secondary squeegee to remove the residue on the lower surface of the stencil.

[0128] Step 4: Apply a pressure of 30 N / cm 2 to the upper surface of the stencil by using a squeegee to extrude, so that the slurry detaches from the groove 5 and is transferred to the surface of the substrate, and the transfer rate in the groove is 95%.

[0129] Step 5: After separating from the plate, sintering is carried out to form a grid line density of 80 lines per sheet, and the line width accuracy is ±0.3 μm.

[0130] Comparative Example 2

[0131] The manufacturing method of a stencil transfer design prepared in this example includes the following steps:

[0132] Step 1: Prepare a stencil with a total thickness of 15 μm. The stencil includes, from top to bottom and stacked in sequence:

[0133] The first layer, an upper wear-resistant and lubricating layer 1 with a thickness of 1 μm and composed of polyimide PI;

[0134] The second layer, a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0135] The third layer is a grooved layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 having a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is formed with 0.1-μm protrusions by laser treatment, and the density of the protrusions is 20 per mm 2 ;

[0136] The fourth layer is a lower wear-resistant and lubricating layer 4 with a thickness of 1 μm and composed of a PI film.

[0137] Step 2: Use silver paste with a viscosity of 8000 cps, and fill the groove 5 from below the screen plate through a nozzle with a pressure of 50 N / cm 2 Meanwhile, the upper squeegee reciprocates and levels with a pressure of 20 N / cm 2 The distance between the squeegee and the nozzle is 0.5 mm.

[0138] Step 3: Level the lower surface of the screen plate by using a secondary squeegee to remove the residue on the lower surface of the screen plate.

[0139] Step 4: Apply a pressure of 30 N / cm 2 to the upper surface of the screen plate by using a squeegee to extrude, so that the slurry detaches from the groove 5 and is transferred to the substrate surface, and the transfer rate in the groove is 95%.

[0140] Step 5: After leaving the plate, it is sintered to form grid lines with a density of 90 per sheet and a line width accuracy of ±0.3 μm.

[0141] Comparative Example 3

[0142] The manufacturing method for screen plate transfer printing design in this embodiment includes the following steps:

[0143] Step 1: Prepare a screen plate with a total thickness of 15 μm, which includes, from top to bottom in sequence:

[0144] The first layer is an upper wear-resistant and lubricating layer 1 with a thickness of 1 μm and composed of polyimide PI;

[0145] The second layer is a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0146] The third layer is a grooved layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 having a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is formed with 0.1-μm protrusions by laser treatment, and the density of the protrusions is 20 per mm 2 ;

[0147] The fourth layer is a lower wear-resistant and lubricating layer 4 with a thickness of 1 μm and composed of a PI film.

[0148] Step 2: Use silver paste with a viscosity of 8000 cps, and fill the groove 5 from below the screen plate through a nozzle with a pressure of 50 N / cm 2The nozzle fills the groove 5 from below the stencil, while the upper squeegee reciprocates and levels at a pressure of 20 N / cm 2 The squeegee and the nozzle are spaced 0.5 mm apart.

[0149] Step 3: Level the lower surface of the stencil by using a secondary squeegee to remove the residue on the lower surface of the stencil.

[0150] Step 4: Apply a pressure of 30 N / cm 2 to the upper surface of the stencil with a squeegee to extrude the paste, causing the paste to separate from the groove 5 and transfer to the surface of the substrate. The transfer rate in the groove is 95%.

[0151] Step 5: After peeling off the stencil, sintering is carried out to form grid lines with a density of 100 lines per sheet and a line width accuracy of ±0.3 μm.

[0152] Comparative Example 4

[0153] This embodiment prepares a manufacturing method for a stencil transfer design, including the following steps:

[0154] Step 1: Prepare a stencil with a total thickness of 15 μm, which includes, from top to bottom in sequence:

[0155] The first layer, an upper wear-resistant and slip-increasing layer 1 with a thickness of 1 μm and composed of polyimide PI;

[0156] The second layer, a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0157] The third layer, a slotted layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The slotted layer 3 is provided with a rectangular cross-section groove 5 with a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is laser-treated to form protrusions with a height of 0.1 μm and a density of 20 protrusions per mm 2 ;

[0158] The fourth layer, a lower wear-resistant and slip-increasing layer 4 with a thickness of 1 μm and composed of a PI film.

[0159] Step 2: Use silver paste with a viscosity of 8000 cps, and fill the groove 5 from below the stencil with a nozzle at a pressure of 50 N / cm 2 while the upper squeegee reciprocates and levels at a pressure of 20 N / cm 2 The squeegee and the nozzle are spaced 0.5 mm apart.

[0160] Step 3: Level the lower surface of the stencil by using a secondary squeegee to remove the residue on the lower surface of the stencil.

[0161] Step 4: Apply a pressure of 30 N / cm 2 to the upper surface of the stencil with a squeegee to extrude the paste, causing the paste to separate from the groove 5 and transfer to the surface of the substrate. The transfer rate in the groove is 95%.

[0162] Step 5: After separation from the substrate, sintering is carried out to form grid lines with a density of 600 lines per sheet and a line width accuracy of ±0.3 μm.

[0163] Comparative Example 5

[0164] This example provides a manufacturing method for screen printing transfer design, including the following steps:

[0165] Step 1: Prepare a screen with a total thickness of 15 μm, which includes the following layers stacked from top to bottom:

[0166] The first layer is an upper wear-resistant and lubricating layer 1 with a thickness of 1 μm, composed of polyimide PI;

[0167] The second layer is a stainless steel metal sealing layer 2 with a thickness of 10 μm;

[0168] The third layer is a grooved layer 3 formed by electroforming in one piece, with a thickness of 4 μm. The grooved layer 3 is provided with a rectangular cross-section groove 5 with a width of 15 μm and a depth of 10 μm. The inner surface of the groove 5 is treated by laser to form protrusions with a height of 0.1 μm and a density of 20 protrusions per mm 2 ;

[0169] The fourth layer is a lower wear-resistant and lubricating layer 4 with a thickness of 1 μm, composed of a PI film.

[0170] Step 2: Use silver paste with a viscosity of 8000 cps to fill the groove 5 from below the screen through a nozzle with a pressure of 50 N / cm 2 , and at the same time, the upper squeegee reciprocates to scrape flat with a pressure of 20 N / cm 2 . The distance between the squeegee and the nozzle is 0.5 mm.

[0171] Step 3: Scrape and level the lower surface of the screen by using a secondary squeegee to remove the residue on the lower surface of the screen.

[0172] Step 4: Apply a pressure of 30 N / cm 2 to the upper surface of the screen by using a squeegee to extrude, so that the slurry separates from the groove 5 and is transferred to the surface of the substrate, and the transfer rate in the groove is 95%.

[0173] Step 5: After separation from the substrate, sintering is carried out to form grid lines with a density of 700 lines per sheet and a line width accuracy of ±0.3 μm.

[0174] Next, the solar cell wafers produced by the screens obtained in the above 1-5 groups of comparative examples (taking a 183.75 cm × 182.2 cm silicon wafer for the solar cell wafer as an example, with a base area of 33471 mm 2 , and removing 4 chamfers) are subjected to performance tests, and the results are as follows:

[0175] Table 2 Performance test results of solar cell wafers produced by the screens obtained in each group of comparative examples

[0176]

[0177] As shown in Table 1 - Table 2, by comparing the data of the examples and the comparative examples, the conversion efficiency of the solar cells is higher than that of Comparative Examples 1 - 5 within the range of the grid line density of 170 - 500 lines per wafer. For the solar cells with the grid line density outside the range of 170 - 500 lines per wafer, the more the number of grid lines, the greater the increase in fill factor is than the loss in open - circuit voltage and short - circuit current, so the efficiency increases; that is, in the direction of denser grid and finer grid, the more the dense grid, the narrower printing width should be theoretically matched. On the one hand, affected by the stable printing width, it is not easy to make it narrower. On the other hand, the narrower the printing, the greater the contact resistance of the metallized alloy of the printing paste. Therefore, there is an inflection point of the maximum number of grid lines.

[0178] In Comparative Examples 1 - 5, because the cumulative printing area is greatly reduced, resulting in a relatively large overall contact and a seriously low fill factor, less than 100 lines are not beneficial on the silicon wafer and the industry is moving towards producing larger wafers. Therefore, the number of lines less than 100 is basically not considered. For more than 500 lines, because the cumulative printing area continues to increase, with the minimum line width currently achievable at an opening of 9μm, the cumulative metallization composite is proportional to the printing area, and the shading area is continuously increasing, resulting in serious short - circuit current losses. Although the loss in fill factor has further increased, the efficiency does not gain further benefits.

[0179] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for making a screen transfer design, characterized in that: The following steps are involved: Step 1: Prepare a screen with a total thickness of 15-200 μm, the screen comprising an upper wear-resistant and slip-increasing layer, a metal sealing layer, a slotted layer and a lower wear-resistant and slip-increasing layer stacked in sequence from top to bottom, the slotted layer is provided with a plurality of grooves at equal intervals, the lower wear-resistant and slip-increasing layer covers the end surface of the unslotted area of ​​the slotted layer, and the inner surface of the groove is sandblasted or laser treated to form a plurality of circular protrusions; Step 2: Fill the slurry into the groove area from below through a nozzle with a nozzle pressure of 50-200N / cm 2 At the same time, use a scraper to apply pressure of 20-70N / cm along the lower edge of the upper surface of the screen. 2 Reciprocating motion is performed below; Step 3: Use a secondary scraper to scrape the lower surface of the screen to remove the slurry residue in the non-groove area; Step 4: Use a scraper to apply 20-100N / cm to the upper surface of the screen. 2 The slurry is squeezed by a pressure to separate from the groove and transfer to the surface of the substrate; Step 5: After leaving the plate, transfer the slurry to the substrate and sinter and solidify it.

2. A method for making a screen transfer design according to claim 1, characterized in that: The groove has a groove width of 3-15 μm and a groove depth of 3-15 μm.

3. A method for making a screen transfer design according to claim 1, characterized in that: The groove cross-section of the groove is selected from at least one of a trapezoidal shape, a circular shape or a rectangular shape.

4. A method for making a screen transfer design according to claim 1, characterized in that: The protrusions have a height of 0.05-0.2 μm, a bottom diameter of 0.05-0.5 μm, and a number of 10-50 / mm 2 .

5. A method for making a screen transfer design according to claim 1, characterized in that: The thickness of the upper wear-resistant and slip-enhancing layer is 1-15 μm, the thickness of the metal sealing layer is 10-150 μm, the thickness of the slotted layer is 5-20 μm, and the thickness of the lower wear-resistant and slip-enhancing layer is 1-15 μm.

6. A method for making a screen transfer design according to claim 1, characterized in that: The slurry viscosity is 5000-20000 cps, the substrate is a solar cell silicon wafer, and the printed grid line density is 170-500 per wafer.

7. A method for making a screen transfer design according to claim 1, characterized in that: A metal transition layer with a thickness of 0.5-3 μm is provided between the metal sealing layer and the slotted layer, and the metal sealing layer and the slotted layer are integrally formed by electroforming.

8. A method for making a screen transfer design according to claim 1, characterized in that: The materials of the upper wear-resistant and slip-enhancing layer and the lower wear-resistant and slip-enhancing layer are selected from any one of PI film and resin, and the material of the metal sealing layer is selected from any one of stainless steel, nickel alloy or copper alloy.

9. A screen, characterized in that: The screen is obtained by the production method of the screen transfer design as described in any one of claims 1 to 8, the total thickness of the screen is 15-200μm, and includes an upper wear-resistant and slip-enhancing layer, a metal sealing layer, a slotted layer and a lower wear-resistant and slip-enhancing layer stacked in sequence from top to bottom, a plurality of grooves are equidistantly provided on the slotted layer, the lower wear-resistant and slip-enhancing layer covers the ungrooved area of ​​the slotted layer, the grooves are 3-15μm wide and 3-15μm deep, the inner surface of the grooves is sandblasted or laser treated to form a plurality of circular protrusions, and a 0.5-3μm metal transition layer is provided between the metal sealing layer and the slotted layer.

10. A printing system for making the screen printing plate according to claim 9, characterized in that: The filling pressure of the nozzle is 50-200N / cm 2 The demoulding pressure of the upper scraper is 20-100N / cm 2 The scraping edge pressure of the lower scraper is 20-70N / cm 2 , the working distance between the upper scraper and the nozzle is 0.5-2mm; The printing system also includes a closed-loop control system for controlling the nozzle pressure and the working distance between the upper scraper and the nozzle. The closed-loop control system is electrically connected to the nozzle, the upper scraper, and the lower scraper, respectively. The curvature radius of the working surface of the upper scraper and the lower scraper is adapted to the total thickness of the screen.

Images