Solar cell screen printing device and printing method

Abstract

The present invention is applicable to the fields of solar cells and screen printing, and provides a screen printing device and a printing method for solar cells. The screen printing device for solar cells includes: a base, a printing platform located above the base for placing the cells; a screen plate is provided directly above the printing platform, and a squeegee is provided above the screen plate; an adjusting device, and a control device connected to the adjusting device. By controlling the screen plate spacing to gradually decrease in the first stroke of solar cell printing and gradually increase in the third stroke, the problem that the grid lines are uneven at the edge of the existing screen printing is solved, and the screen plate spacing remains unchanged in the second stroke of printing the middle solar cells, and the screen plate spacing in the first stroke and the third stroke is greater than the screen plate spacing in the second stroke. Compared with the existing solution of increasing the screen plate spacing, the gram weight of the printing paste is reduced, and the problem of increased gram weight of the paste caused by the existing increase in the screen plate spacing is solved.

Description

Technical Field

[0001] The present invention belongs to the fields of solar cells and screen printing, and particularly relates to a solar cell screen printing device and a printing method. Background Art

[0002] In the photovoltaic industry, the cost of the screen printing paste has always accounted for more than 30% of the cost of preparing photovoltaic cells. Therefore, how to reduce the consumption of the screen plate and the paste while ensuring the printing quality and conversion efficiency has become a key factor in reducing costs.

[0003] The traditional printing mode uses a scheme with a fixed screen plate spacing (the screen plate spacing is the height between the screen plate and the printing platform) for printing. For example Figure 1 H1, H2, and H3 in it all represent the screen plate spacing. H1 refers to the screen plate spacing at the starting position, H2 represents the screen plate spacing at the intermediate position of solar cell printing, and H3 represents the screen plate spacing at the knife retraction position. In the prior art, the screen plate spacing is the same throughout the printing process. In this printing mode, there will be differences in the tension and printing deformation amount between the starting and ending positions of the squeegee for the printed grid lines at the edge because they are close to the screen plate frame, and the parameter of the screen plate spacing often causes differences in the position of the fixed points where the edge is close to the screen plate, resulting in a situation where the line width of the fine grid lines closest to the screen plate edge on the battery is wider than the specification, often causing abnormal or poor printing of solar cells.

[0004] Therefore, in the current printing mode, the screen plate spacing is the same height from the printing starting position to the ending position, and it is impossible to ensure the uniformity of the width of the printed grid lines. To solve this problem, it is often necessary to increase the screen plate spacing, but this will bring the problem of increased paste weight due to the increase in the screen plate spacing. Summary of the Invention

[0005] Embodiments of the present invention provide a solar cell screen printing device, aiming to solve the problem that the existing screen printing cannot ensure the uniformity of the grid line width, and the problem of increased paste weight caused by increasing the screen plate spacing.

[0006] Embodiments of the present invention are implemented as follows. A solar cell screen printing device is provided, and the solar cell screen printing device includes:

[0007] A base, and a printing platform located above the base for placing the battery;

[0008] Above the printing platform, there is a stencil, and above the stencil, there is a squeegee. The starting position of the forward stroke of the squeegee printing on the stencil is the starting position, and the ending position of the forward stroke of the squeegee printing on the stencil is the retracting position. Among them, there are a first position and a second position between the starting edge of the solar cell printing and the ending edge of the solar cell printing. The first position is close to the starting edge, and the second position is close to the ending edge. The printing stroke of the solar cell includes: a first stroke from the starting edge to the first position, a second stroke from the first position to the second position, and a third stroke from the second position to the ending edge.

[0009] An adjusting device for adjusting the stencil spacing, where the stencil spacing is the distance between the stencil and the printing platform.

[0010] A control device connected to the adjusting device. The control device is used to gradually reduce the stencil spacing during the first stroke of the solar cell printing, keep the stencil spacing unchanged during the second stroke, and gradually increase the stencil spacing during the third stroke.

[0011] The stencil spacing in the first stroke and the stencil spacing in the third stroke are both greater than the stencil spacing in the second stroke.

[0012] Furthermore, the control device is also used to keep the stencil spacing unchanged when moving from the starting position to the starting edge, keep the stencil spacing unchanged when moving from the ending edge to the retracting position, and the stencil spacing at the starting position is the same as the stencil spacing at the retracting position.

[0013] Furthermore, the spacing of the first stroke is equal to the spacing of the third stroke; and / or, the ratio of the spacing of the first stroke to the spacing of the total printing stroke of the solar cell is 2%-5%.

[0014] Furthermore, the stencil spacing at the starting position is equal to the stencil spacing at the retracting position; and / or, the ratio of the spacing from the starting position to the starting edge to the spacing of the total printing stroke of the solar cell is 3%-20%.

[0015] Furthermore, the control device controls the stencil spacing to decrease linearly during the first stroke and increase linearly during the third stroke, and the slope of the linear decrease of the stencil spacing is the same as the slope of the linear increase of the stencil spacing.

[0016] Further, the adjusting device includes a first screw rod slider module and a second screw rod slider module disposed on the base and located on both sides of the screen plate. A first connecting member for fixedly connecting one side of the screen plate is provided on the first screw rod slider module, and a second connecting member for fixedly connecting the other side of the screen plate is provided on the second screw rod slider module. The first screw rod slider module and the second screw rod slider module move simultaneously to drive the screen plate to move in the vertical direction.

[0017] Further, the first screw rod slider module includes a first screw rod bracket, a first screw rod located on the first screw rod bracket, and a first motor for driving the first screw rod to move in the vertical direction.

[0018] Further, the first connecting member includes a first connecting block connected to the first screw rod. Fixing blocks for fixing the screen plate are provided on both sides of the first connecting block. Guide sliders are provided on the fixing blocks, and guide rails cooperating with the guide sliders are provided on the first screw rod bracket.

[0019] Further, the adjusting device includes a second screw rod bracket, a second screw rod located on the second screw rod bracket, and a second motor for driving the second screw rod to move up and down in the vertical direction. The printing platform is fixedly connected to the second screw rod, and the second motor drives the printing platform to move up and down in the vertical direction.

[0020] Further, the adjusting device further includes a linear slide rail moving in the horizontal direction. A second slider moving along the linear slide rail is provided on the linear slide rail. The second slider is fixedly connected to the second screw rod bracket and is used to drive the printing platform to move in the horizontal direction.

[0021] An embodiment of the present invention further provides a printing method applied to the above-mentioned solar cell screen printing device, which is characterized in that the printing method includes the following steps:

[0022] Obtain the position of the squeegee and control the squeegee to move to the starting position;

[0023] The squeegee presses down on the screen plate;

[0024] During the process of the squeegee squeezing the paste from the starting position to the retracting position, control the screen plate spacing to gradually decrease in the first stroke of solar cell printing, keep the screen plate spacing unchanged in the second stroke, and control the screen plate spacing to gradually increase in the third stroke.

[0025] The screen printing device for solar cells according to the embodiment of the present invention solves the problem that the grid lines are uneven at the edge of the existing screen printing by gradually reducing the distance between the screen plates during the first stroke of solar cell printing and gradually increasing the distance between the screen plates during the third stroke, and keeps the distance between the screen plates unchanged during the second stroke of printing the middle solar cells. Moreover, the distances between the screen plates in the first stroke and the third stroke are both greater than that in the second stroke. Compared with the existing scheme of increasing the distance between the screen plates, the weight of the printing paste is reduced, and the problem of increased weight of the paste caused by the existing increase in the distance between the screen plates is solved. Brief Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the change in the distance between the screen plates of the screen printing device for solar cells according to Embodiment 1 of the present invention;

[0027] Figure 2 It is a schematic structural diagram of Embodiment 5 of the screen printing device for solar cells according to the embodiment of the present invention;

[0028] Figure 3 It is another schematic structural diagram of Embodiment 5 of the screen printing device for solar cells according to the embodiment of the present invention;

[0029] Figure 4 It is a rear view of Embodiment 5 of the screen printing device for solar cells according to the embodiment of the present invention;

[0030] Figure 5 It is a schematic structural diagram of the screen printing device for solar cells according to the embodiment of the present invention;

[0031] Figure 6 It is a schematic structural diagram of Embodiment 6 of the screen printing device for solar cells according to the embodiment of the present invention;

[0032] Figure 7 It is another schematic structural diagram of Embodiment 6 of the screen printing device for solar cells according to the embodiment of the present invention;

[0033] Figure 8 It is a schematic curve diagram of the change in the distance between the screen plates of the screen printing device for solar cells according to the embodiment of the present invention;

[0034] Figure 9 It is a schematic curve diagram of the change in the distance between the screen plates of the screen printing device for solar cells according to the embodiment of the present invention.

[0035] Description of the Reference Numerals in the Drawings

[0036] 1. Base; 2. Printing Guide Rail;

[0037] 10. Screen Plate; 11. First Connecting Block; 12. Fixed Block; 13. Guide Slide Block;

[0038] 20. Printing Platform; 21. Solar Cell;

[0039] 31. Second lead screw bracket; 32. Second motor; 33. Second lead screw;

[0040] 40. Linear slide rail; 41. Slide block;

[0041] 50. First lead screw slider module; 51. First lead screw bracket; 52. First lead screw; 53. First motor; 54. Guide slide rail;

[0042] 60. Second lead screw slider module. Detailed implementation manner

[0043] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] The present invention provides a screen printing device for solar cells. By controlling the screen plate spacing to gradually decrease in the first stroke of solar cell printing and gradually increase in the third stroke, the problem that the grid lines are uneven at the edge of the existing screen printing is solved. And the screen plate spacing remains unchanged in the second stroke of printing the middle solar cells, and the screen plate spacing in the first stroke and the third stroke is greater than the screen plate spacing in the second stroke. Compared with the existing scheme of increasing the screen plate spacing, the gram weight of the printing paste is reduced, and the problem of increased gram weight of the paste caused by the existing increase in the screen plate spacing is solved.

[0045] Embodiment 1

[0046] As Figure 1As shown in the figure, this embodiment provides a screen printing device for solar cells. The screen printing device for solar cells includes a base 1, and the base 1 is provided with a printing platform 20 for placing the battery 21; a screen plate 10 is provided directly above the printing platform 20, and a squeegee is provided above the screen plate 10; the starting position of the forward stroke of the squeegee printing on the screen plate 10 is the starting position, and the ending position of the forward stroke of the squeegee printing on the screen plate 10 is the retracting position; wherein, a first position and a second position are provided between the starting edge of the solar cell printing and the ending edge of the solar cell printing, the first position is close to the starting edge, and the second position is close to the ending edge; the printing stroke of the solar cell includes: a first stroke from the starting edge to the first position, a second stroke from the first position to the second position, and a third stroke from the second position to the ending edge; an adjusting device for adjusting the screen plate spacing, and the screen plate spacing is the distance between the screen plate and the printing platform; a control device, the control device is connected to the adjusting device, and the control device is used to gradually reduce the screen plate spacing during the first stroke of the solar cell printing, keep the screen plate spacing unchanged during the second stroke, and gradually increase the screen plate spacing during the third stroke; the screen plate spacing in the first stroke and the screen plate spacing in the third stroke are both greater than the screen plate spacing in the second stroke.

[0047] Referring to Figure 1 , in this embodiment, the starting position of the squeegee corresponds to P1, the retracting position of the squeegee corresponds to P3, the middle position of the solar cell printing corresponds to P2, the starting edge of the solar cell printing is P4, the ending edge of the solar cell printing is P7, the first position corresponds to P5, and the second position corresponds to P6.

[0048] Among them, the entire printing stroke is from P1 to P3, specifically including the starting position P1 of the squeegee to the starting edge P4 of the solar cell printing (that is, P1 - P4), the printing stroke of the solar cell (P4 - P7), and the ending edge P7 to the retracting position P3 of the squeegee (that is, P7 - P3). The printing stroke of the solar cell is from the starting edge P4 of the solar cell printing to the ending edge P7 of the solar cell printing; it includes a first stroke (P4 - P5), a second stroke (P5 - P6), and a third stroke (P6 - P7).

[0049] During the printing stroke of the solar cell in this embodiment, the screen plate spacing is gradually reduced during the first stroke, kept unchanged during the second stroke, and gradually increased during the third stroke. Among them, the screen plate spacing in the first stroke and the third stroke are both greater than the screen plate spacing in the second stroke.

[0050] In this embodiment, the control device is a PLC controller. The PLC controller stores a preset adjustment rule for the screen plate spacing and can adjust the PLC control program according to the printing needs to dynamically adjust the screen plate spacing during the printing process of the squeegee on the screen plate 10.

[0051] The screen printing device for solar cells in this embodiment controls the screen plate spacing to gradually decrease in the first stroke of solar cell printing and gradually increase in the third stroke. Because of the increase in the screen plate spacing, the rebound effect of the large deformation of screen plate printing is better, and the line width is relatively thin, which solves the problem that the grid lines are uneven at the edge of the existing screen printing. And the screen plate spacing remains unchanged in the second stroke of printing the middle solar cell, and the screen plate spacings in the first stroke and the third stroke are both greater than the screen plate spacing in the second stroke. Compared with the solution of increasing the screen plate spacing to solve the problem of uneven grid lines in printing in the prior art, the gram weight of the printing paste is reduced because, during the printing process, the increase in the screen plate spacing will cause more printing paste to be squeezed down. Therefore, this application solves both the problem of uneven grid lines at the printing edge and the problem of increased gram weight of the paste. The screen printing device for solar cells in this embodiment improves the printing efficiency of the battery on the one hand and reduces the loss of the paste on the other hand.

[0052] Embodiment 2

[0053] On the basis of the above-mentioned Embodiment 1, this embodiment provides a screen printing device for solar cells. Among them, the control device is further used to keep the screen plate spacing unchanged when moving from the starting position to the starting edge, and keep the screen plate spacing unchanged when moving from the ending edge to the retracting position of the knife. The screen plate spacing at the starting position is the same as the screen plate spacing at the retracting position of the knife.

[0054] In this embodiment, the screen plate spacing at the starting position P1 of the squeegee is H1, the screen plate spacing at the retracting position P3 of the squeegee is H3, and the screen plate spacings at the first position H5 and the second position H6 are both H2.

[0055] During the forward printing process of the squeegee, during the printing process from the starting position P1 to P4 of the squeegee, the screen plate spacing H1 remains unchanged, that is, the screen plate spacing at the starting edge P4 of solar cell printing is H1. And during the printing process from the end P7 of solar cell printing to the retracting position P3 of the squeegee, the screen plate spacing H3 remains unchanged, that is, the screen plate spacing at the ending edge P7 of solar cell printing is H3. And H1 and H3 are the same. Among them, H1 is greater than H2, and H1 is greater than the screen plate spacings in the first stroke, the second stroke, and the third stroke respectively.

[0056] In the screen printing device for solar cells of this embodiment, during the printing strokes from the starting position to the starting edge of solar cell printing and from the ending edge of solar cell printing to the knife retraction position, the screen plate spacing remains unchanged. Compared with the screen plate spacing during the solar cell printing stroke, the screen plate spacing at the starting position and the knife retraction position is increased. Because when the screen plate spacing is too small, the pressure is relatively large, and a deeper squeegee depth will cause burr problems. However, the printing device of this embodiment increases the screen plate spacing at the starting position and the knife retraction position, with relatively smaller pressure, solving the burr problem at the edges of solar cell printing and further improving the printing efficiency of solar cells.

[0057] Embodiment 3

[0058] Referring to Figure 7 , on the basis of the above-mentioned Embodiment 1 or 2, this embodiment provides a screen printing device for solar cells, wherein the spacing of the first stroke is equal to that of the third stroke; the ratio of the spacing of the first stroke to the spacing of the total solar cell printing stroke is 2% - 5%.

[0059] In this embodiment, the spacing of the total solar cell printing stroke includes the spacing sums of the first stroke, the second stroke, and the third stroke, that is, the spacing from P4 to P7, denoted as P4 - P7.

[0060] In this embodiment, the spacing from P4 to P5 is the same as the spacing from P6 to P7. Among them, the spacing from P4 to P5 is denoted as P4 - P5, and the spacing from P6 to P7 is denoted as P6 - P7. By making the spacing of P4 - P5 the same as that of P6 - P7 in this embodiment, while ensuring printing uniformity and reducing the paste, the control program is simple and reliable, and the device structure is more simple, reducing costs.

[0061] It should be noted that, referring to Figure 1 , the spacing of the first stroke is denoted as: P4 - P5; the spacing of the total solar cell printing stroke is denoted as: P4 - P7; among them, the ratio of the spacing of the first stroke to the spacing of the total solar cell printing stroke is 2% - 5%, that is, the ratio of P4 - P5 / P4 - P7 is 2% - 5%. Through experimental analysis, when the ratio of the spacing from the starting edge P4 of solar cell printing to the first position P5 to the printing stroke spacing of solar cells is 3%, the grid lines at the edges of solar cell printing can be ensured to be uniform, and the loss of the paste is relatively low. It can be understood that the ratio of P6 - P7 / P4 - P7 is 2% - 5%.

[0062] This ratio is for an empirical model. When printing using a printing method with a constant height, the starting and ending knife positions of the printing have a significantly wider width within 3 mm of the first grid line, but it drops sharply to the average line after 4 - 5 mm. The first grid line is generally 2 mm away from the edge of the silicon wafer, so a range of 2 - 5% is given based on calculations.

[0063] Furthermore, the screen plate spacing at the starting position and the ending knife position is equal; the ratio between the travel spacing from the starting position to the starting edge and the total travel of the solar cell printing is 3% - 20%.

[0064] In this embodiment, the spacing from the starting position P1 to the starting edge P4 of the solar cell printing is denoted as P1 - P4. Among them, the ratio of P1 - P4 / P4 - P7 is 3% - 20%. Through experimental analysis, when the ratio of the spacing between the starting position P1 of the squeegee and the starting edge P4 of the solar cell printing to the travel spacing of the entire solar cell printing is 10%, the burrs at the edge of the solar cell printing can be significantly reduced, and the yield of the solar cell printing can be improved. It can be understood that the ratio of P7 - P3 / P4 - P7 is 3% - 20%.

[0065] This ratio is for an empirical model. When printing using a printing method with a constant height, burr problems occur within 3 mm of the first grid line at the starting and ending knife positions of the printing, but the burr problems gradually disappear after 5 - 6 mm. The first grid line is generally 2 mm away from the edge of the silicon wafer, so a range of 3 - 20% is given based on calculations.

[0066] The solar cell printing device of this embodiment can effectively solve the problems of uneven grid lines and increased paste weight in solar cell printing, and effectively solve the burr problem at the edge of the solar cell printing, improving the yield of solar cell printing, by setting the proportional relationship between the spacing of the first travel and the third travel and the travel spacing of the solar cell printing, and the proportional relationship between the starting position of the squeegee and the starting edge of the solar cell printing and the entire travel of the solar cell printing.

[0067] Embodiment 4

[0068] Based on the above Embodiment 3, this embodiment provides a solar cell screen printing device. Among them, the control device controls the screen plate spacing to decrease linearly in the first travel and increase linearly in the third travel, and the slope of the linear decrease in the screen plate spacing is the same as the slope of the linear increase in the screen plate spacing.

[0069] Refer to Figure 8It can be known that in this embodiment, when the starting edge P4 of the solar cell printing reaches the first position P5, the stencil pitch decreases linearly. Among them, the stencil pitch at P4 is H1, and the stencil pitch at the first position P5 is H2. Specifically, let the distance between P4 and P5 be X1, Y1 = H1 - H2 = 0.1 - 1.5 mm, and the printing speed be S. At this time, Y1 = aX1 / S. When the printing speed, X1, and Y1 are determined, a can be obtained. a is the slope of the linear decrease in the stencil pitch. According to the slope, the linear function of the stencil pitch change in the first stroke can be obtained. For example: Y = aX. The linear function curve is obtained according to the change trend of the stencil pitch corresponding to the points in different strokes. Therefore, according to this linear function of the stencil pitch change, the adjustment range and amplitude of the stencil pitch change in different strokes can be obtained.

[0070] It is known through experiments that when the difference in the stencil pitch between the starting edge and the first position is 0.5 mm, the grid lines at the edge are uniform, and the gram weight of the paste can be reduced by about 5 - 15%. According to the experimental measurement, the difference range of the stencil pitch between the starting edge and the first position is obtained.

[0071] It can be understood that when the printing of the solar cell reaches the end edge P7 from the second position P6, the stencil pitch increases linearly. Among them, the stencil pitch at the second position P6 is H1, and the stencil pitch at the end edge P7 of the solar cell printing is H2. Specifically, let the distance between P6 and P7 be X2, Y2 = H1 - H2 = 0.1 - 1.5 mm, and the printing speed be S. At this time, Y2 = bX2 / S. When the printing speed, X2, and Y2 are determined, b can be obtained. b is the slope of the linear increase in the stencil pitch. According to the slope, the linear function of the stencil pitch change in the third stroke can be obtained. For example: Y = bX. The linear function curve is obtained according to the change trend of the stencil pitch corresponding to the points in different strokes. Therefore, according to this linear function of the stencil pitch change, the adjustment range and amplitude of the stencil pitch change in different strokes can be obtained.

[0072] In this embodiment, the absolute values of the slope a and the slope b are the same, that is, the decreasing amplitude of the stencil pitch in the first stroke is the same as the increasing amplitude of the stencil pitch in the third stroke. The increasing or decreasing amplitude of the stencil pitch is calculated through experiments to ensure the yield of the solar cell printing.

[0073] In another embodiment, the control device controls the stencil pitch to decrease non-linearly in the first stroke and increase non-linearly in the third stroke.

[0074] Refer to Figure 9, in this embodiment, when the starting edge P4 of the solar cell printing reaches the first position P5, the stencil pitch decreases non-linearly. When it reaches the ending edge P7 of the solar cell printing at the second position P6, the stencil pitch increases non-linearly. During the solar cell printing, the change in the stencil pitch in the first stroke conforms to the curve decreasing trend, and the change in the stencil pitch in the third stroke conforms to the curve increasing trend. Among them, the function curve of the non-linearly decreasing stencil pitch in the first stroke and the function curve of the non-linearly increasing stencil pitch in the third stroke are symmetrically arranged about the middle position of the solar cell printing. For example: the function curve of the stencil pitch change is Y = ax 2 . The function curve is obtained based on the change trend of the stencil pitch corresponding to the points in different strokes. The change trend and range of the stencil pitch are adjusted by adjusting the change of the exponent a. It should be noted that by adjusting the exponent a to adjust the change trend of the stencil pitch and controlling the change of the exponent a through the control program, the control program is simple, the device structure is more simple, and the cost is reduced.

[0075] It can be understood that in other embodiments, the change trend of the stencil pitch in the first stroke and the third stroke can also be other function curves, which are not specifically limited in this embodiment. The stencil pitch can be dynamically adjusted according to the preset trend within the printing stroke according to the printing requirements.

[0076] The solar cell printing device of this embodiment solves the problem of uneven printing grid lines of the solar cell by controlling the stencil pitch to decrease linearly in the first stroke and increase linearly in the third stroke, and effectively reduces the paste loss caused by increasing the stencil pitch, improving the yield of the solar cell printing.

[0077] Embodiment 5

[0078] Referring to Figures 2 to 4 , on the basis of the above-mentioned first embodiment, this embodiment provides a solar cell screen printing device, which adjusts the stencil pitch by controlling the movement of the stencil in the vertical direction. Specifically, the adjusting device includes a first lead screw slider module 50 and a second lead screw slider module 60 provided on the base 1 and located on both sides of the stencil. A first connecting member for fixedly connecting one side of the stencil 10 is provided on the first lead screw slider module 50, and a second connecting member for fixedly connecting the opposite side of the stencil is provided on the second lead screw slider module 60. The first lead screw slider module and the second lead screw slider module move simultaneously to drive the stencil to move in the vertical direction to adjust the stencil pitch.

[0079] In this embodiment, a circular printing platform 20 is provided on the base 1, and a plurality of batteries 21 can be provided on the printing platform 20. After the printing of the previous battery 21 is completed, the printing platform 20 can be driven to rotate, so as to control the next battery 21 to be directly below the stencil 10. The stencil 10 is connected to the first lead screw slider module 50 and the second lead screw slider module 60 through a first connecting member and a second connecting member, and the stencil 10 is driven to move up and down in the vertical direction by the first lead screw slider module 50 and the second lead screw slider module 60.

[0080] Among them, the first lead screw slider module 50 includes a first lead screw bracket 51, a first lead screw 52 located on the first lead screw bracket 51, and a first motor 53 for driving the first lead screw 52 to move in the vertical direction. The second lead screw slider module has the same structure as the first lead screw slider module. This embodiment will not be elaborated here.

[0081] The first connecting member includes a first connecting block 11 connected to the first lead screw. Fixing blocks 12 for fixing the stencil 10 are provided on both sides of the first connecting block 11. Guide sliders 13 are provided on each fixing block 12, and two guide rails 54 cooperating with the guide sliders 13 are provided on the first lead screw bracket 51.

[0082] The first motor 53 drives the first lead screw 52 to move up and down in the vertical direction. The first connecting block 11 moves up and down in the vertical direction under the drive of the first lead screw 52. At the same time, the guide slider 13 moves on the guide rail 54. The cooperation between the guide slider 13 and the guide rail 54 plays a guiding role to prevent the stencil 10 from moving in the horizontal direction. The second connecting member has the same structure as the first connecting member. This embodiment will not be elaborated here.

[0083] In this embodiment, the control device is connected to the first lead screw slider module 50 and the second lead screw slider module 60, and the first lead screw slider module 50 and the second lead screw slider module 60 are controlled by the control device to move according to a preset program rule.

[0084] In the solar cell screen printing device of this embodiment, the stencil is driven to move up and down in the vertical direction by the cooperation of the first lead screw slider module and the second lead screw slider module to dynamically adjust the stencil spacing. Specifically, the stencil spacing is gradually reduced in the first stroke of solar cell printing, the stencil spacing is kept unchanged in the second stroke, and the stencil spacing is gradually increased in the third stroke, effectively avoiding the uneven printing grid lines of solar cells, and effectively reducing the paste loss caused by increasing the stencil spacing, and improving the yield of solar cell printing.

[0085] Embodiment 6

[0086] Refer to Figures 5 to 7, on the basis of the above-mentioned first embodiment, this embodiment provides a screen printing device for solar cells. Among them, the adjusting device includes a second screw rod bracket 31, a second screw rod 33 located on the second screw rod bracket 31, and a second motor 32 that drives the second screw rod 33 to move up and down in the vertical direction. A printing platform 20 is fixedly connected to the second screw rod 33.

[0087] In this embodiment, the second motor 32 drives the second screw rod 33 to move in the vertical direction, thereby driving the printing platform 20 to move in the vertical direction, and further adjusting the distance between the screen plate 10 and the printing platform 20.

[0088] Furthermore, the adjusting device further includes a linear slide rail 40 that moves in the horizontal direction. A slider 41 that moves along the linear slide rail 40 is provided on the linear slide rail 40. The slider 41 is fixedly connected to the second screw rod bracket 31 and is used to drive the printing platform 20 to move in the horizontal direction.

[0089] In this embodiment, the slider 41 can drive the printing platform 20 to move on the linear slide rail 40. Two printing platforms 20 can be arranged on the linear slide rail 40 to facilitate improving the feeding efficiency of the battery.

[0090] Specifically, a printing guide rail 2 is further provided above the screen plate 10. A squeegee is provided on the printing guide rail 2. A first linear module for controlling the squeegee to move along the printing guide rail 2 and a second linear module for controlling the squeegee to move in the vertical direction are also provided on the printing guide rail 2. The control device is connected to the first linear module and the second linear module. During printing, the control device controls the squeegee to press down on the screen plate 10 and move from the starting position to the retracting position at a preset speed, and at the same time controls the adjusting device to adjust the screen plate distance according to a preset rule to complete a one-way stroke of solar cell printing.

[0091] The screen printing device for solar cells in this embodiment drives the printing platform to move up and down in the vertical direction through the adjusting device to realize dynamic adjustment of the distance between the screen plates. Specifically, the screen plate distance is gradually reduced during the first stroke of solar cell printing, the screen plate distance is kept unchanged during the second stroke, and the screen plate distance is gradually increased during the third stroke, effectively avoiding the uneven printing grid lines of solar cells, and effectively reducing the paste loss caused by increasing the screen plate distance, and improving the yield of solar cell printing. Compared with the existing method of printing batteries with a fixed screen plate height, on the one hand, it improves the printing efficiency of the battery, and on the other hand, it reduces the paste loss.

[0092] Embodiment 7

[0093] This embodiment provides a screen printing method for solar cells, and this method includes the following steps:

[0094] Obtain the position of the squeegee and control the squeegee to move to the starting position;

[0095] The squeegee presses down to the screen plate;

[0096] During the movement of the squeegee from the starting position to extrude the paste to the retracting position, the screen plate spacing is gradually reduced in the first stroke of the solar cell printing, remains unchanged in the second stroke, and is gradually increased in the third stroke.

[0097] In this embodiment, the position of the squeegee is obtained, and the position of the squeegee is moved to the starting position. And the screen plate spacing is adjusted to a preset initial position, where the initial position and the change curve of the screen plate spacing are preset in advance.

[0098] Refer to Figure 1 , in this embodiment, the starting position of the squeegee corresponds to P1, the retracting position of the squeegee corresponds to P3, the intermediate position of the solar cell printing corresponds to P2, the starting edge of the solar cell printing is P4, the ending edge of the solar cell printing is P7, the first position corresponds to P5, and the second position corresponds to P6.

[0099] Among them, the entire printing stroke includes the starting position P1 of the squeegee to the starting edge P4 of the solar cell printing (i.e., P1 - P4), the printing stroke of the solar cell (P4 - P7), and the ending edge P7 to the retracting position P3 of the squeegee (i.e., P7 - P3). The printing stroke of the solar cell is from the starting edge P4 of the solar cell printing to the ending edge P7 of the solar cell printing; it includes the first stroke (P4 - P5), the second stroke (P5 - P6), and the third stroke (P6 - P7).

[0100] During the printing stroke of the solar cell in this embodiment, the screen plate spacing is gradually reduced in the first stroke, remains unchanged in the second stroke, and is gradually increased in the third stroke. Among them, the screen plate spacings in the first stroke and the third stroke are both greater than the screen plate spacing in the second stroke.

[0101] In this embodiment, the control device is a PLC controller. The adjustment rules of the preset screen plate spacing are stored in the PLC controller, and the PLC control program can be adjusted according to the printing needs to realize the dynamic adjustment of the screen plate spacing during the printing process of the squeegee on the screen plate 10.

[0102] The screen printing method of the solar cell in this embodiment solves the problem that the grid lines are uneven at the edge of the existing screen printing by gradually reducing the screen distance in the first stroke of the solar cell printing and gradually increasing the screen distance in the third stroke. And the screen distance remains unchanged in the second stroke of the middle solar cell printing. Also, the screen distances in the first and third strokes are both greater than the screen distance in the second stroke. Compared with the existing solution of increasing the screen distance, the gram weight of the printing paste is reduced, and the problem of increased paste gram weight caused by increasing the screen distance is solved. The screen printing device of this embodiment improves the printing efficiency of the battery on the one hand and reduces the loss of the paste on the other hand.

[0103] Embodiment 8

[0104] Based on the above Embodiment 7, this embodiment provides a screen printing method for solar cells. Wherein, the printing method further includes keeping the screen distance unchanged when controlling from the starting position to the starting edge, and keeping the screen distance unchanged when controlling from the ending edge to the retracting position of the knife. The screen distances at the starting position and the retracting position of the knife are the same.

[0105] In this embodiment, the screen distance at the starting position P1 of the squeegee is H1, the screen distance at the retracting position P3 of the squeegee is H3, and the screen distance at the first position H5 is H2.

[0106] During the printing process from the starting position P1 to P4 of the squeegee, the screen distance H1 remains unchanged, that is, the screen distance at the starting edge P4 of the solar cell printing is H1. And during the printing process from P7 to the retracting position P3 of the squeegee, the screen distance H3 remains unchanged, that is, the screen distance at the ending edge P7 of the solar cell printing is H3. And H1 and H3 are the same. Wherein, H1 is greater than H2, and H1 is respectively greater than the screen distances in the first, second, and third strokes.

[0107] The screen printing method of the solar cell in this embodiment keeps the screen distance unchanged during the printing strokes from the starting position to the starting edge of the solar cell printing and from the ending edge of the solar cell printing to the retracting position of the knife. Compared with the screen distance in the solar cell printing stroke, the screen distances at the starting position and the retracting position of the knife are increased, the problem of burrs at the edge of the solar cell printing is solved, and the printing efficiency of the solar cell is improved.

[0108] The screen printing device for solar cells of the present invention solves the problem that the grid lines are uneven at the edges in the existing screen printing by controlling the gradual reduction of the stencil pitch in the first stroke of solar cell printing and the gradual increase of the stencil pitch in the third stroke, and keeps the stencil pitch unchanged in the second stroke of intermediate solar cell printing. Moreover, the stencil pitches in the first and third strokes are both greater than that in the second stroke. Compared with the existing solution of increasing the stencil pitch, the gram weight of the printing paste is reduced, and the problem of increased gram weight of the paste caused by increasing the stencil pitch is solved. By keeping the stencil pitch unchanged during the printing strokes from the starting position to the starting edge of solar cell printing and from the ending edge of solar cell printing to the knife retraction position, the stencil pitches at the starting position and the knife retraction position are increased compared with the stencil pitch during the solar cell printing stroke, solving the problem of burrs at the edges of solar cell printing and improving the efficiency of solar cell printing.

[0109] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, 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 screen printing device for solar cells, characterized in that, the screen printing device for solar cells includes: a base, and a printing platform for placing solar cells is provided on the base; a screen plate is provided directly above the printing platform, a squeegee is provided above the screen plate, and a printing guide rail is also provided above the screen plate; the position where the forward stroke of the squeegee printing on the screen plate starts is the starting position, and the position where the forward stroke of the squeegee printing on the screen plate ends is the retracting position; wherein, a first position and a second position are provided between the starting edge of the solar cell printing and the ending edge of the solar cell printing, the first position is close to the starting edge, and the second position is close to the ending edge; the printing stroke of the solar cell includes: a first stroke from the starting edge to the first position, a second stroke from the first position to the second position, and a third stroke from the second position to the ending edge; an adjusting device for adjusting the screen plate spacing, and the screen plate spacing is the distance between the screen plate and the printing platform; a control device, the control device is connected to the adjusting device, and the control device is used to control the screen plate spacing to gradually decrease during the first stroke of the solar cell printing, keep the screen plate spacing unchanged during the second stroke, and control the screen plate spacing to gradually increase during the third stroke; the screen plate spacing in the first stroke and the screen plate spacing in the third stroke are both greater than the screen plate spacing in the second stroke.

2. The screen printing device for solar cells according to claim 1, characterized in that, the control device is further used to control the screen plate spacing to remain unchanged when moving from the starting position to the starting edge, and / or, the control device is further used to control the screen plate spacing to remain unchanged when moving from the ending edge to the retracting position, and the screen plate spacing at the starting position is the same as the screen plate spacing at the retracting position.

3. The screen printing device for solar cells according to claim 1, characterized in that, the spacing in the first stroke is equal to the spacing in the third stroke; and / or, the ratio of the spacing in the first stroke to the spacing of the total printing stroke of the solar cell is 2% - 5%.

4. The screen printing device for solar cells according to claim 1, characterized in that, the screen plate spacing at the starting position is equal to the screen plate spacing at the retracting position; and / or, the ratio of the spacing from the starting position to the starting edge to the spacing of the total printing stroke of the solar cell is 3% - 20%.

5. The screen printing device for solar cells according to claim 3, characterized in that, the control device controls the screen plate spacing to decrease linearly during the first stroke and controls the screen plate spacing to increase linearly during the third stroke, and the slope of the linear decrease of the screen plate spacing is the same as the slope of the linear increase of the screen plate spacing.

6. The screen printing device for solar cells according to claim 1, characterized in that, The adjusting device includes a first lead screw slider module and a second lead screw slider module which are arranged on the base and located on both sides of the screen plate. A first connecting piece for fixedly connecting one side of the screen plate is arranged on the first lead screw slider module, and a second connecting piece for fixedly connecting the other side of the screen plate is arranged on the second lead screw slider module. The first lead screw slider module and the second lead screw slider module move simultaneously to drive the screen plate to move in the vertical direction.

7. The solar cell screen printing device according to claim 6, wherein the first lead screw slider module includes a first lead screw bracket, a first lead screw located on the first lead screw bracket, and a first motor for driving the first lead screw to move in the vertical direction.

8. The solar cell screen printing device according to claim 7, wherein the first connecting piece includes a first connecting block connected to the first lead screw. Fixing blocks for fixing the screen plate are arranged on both sides of the first connecting block. Guide sliders are arranged on the fixing blocks, and guide rails matched with the guide sliders are arranged on the first lead screw bracket.

9. The solar cell screen printing device according to claim 1, wherein the adjusting device includes a second lead screw bracket, a second lead screw located on the second lead screw bracket, and a second motor for driving the second lead screw to move up and down in the vertical direction. The printing platform is fixedly connected to the second lead screw, and the second motor drives the printing platform to move up and down in the vertical direction.

10. The solar cell screen printing device according to claim 9, wherein the adjusting device further includes a linear slide rail moving in the horizontal direction. A second slider moving along the linear slide rail is arranged on the linear slide rail. The second slider is fixedly connected to the second lead screw bracket and is used for driving the printing platform to move in the horizontal direction.

11. A printing method applied to the solar cell screen printing device according to any one of claims 1 to 10, characterized in that, The printing method includes the following steps: Obtain the position of the squeegee and control the squeegee to move to the starting position; The squeegee presses down to the screen plate; During the process of the squeegee squeezing the paste from the starting position to the retracting position, control the screen plate spacing to gradually decrease in the first stroke of solar cell printing, keep the screen plate spacing unchanged in the second stroke, and control the screen plate spacing to gradually increase in the third stroke.

Images