TWI641498B - Screen printing device and substrate printing method for printing flat substrate, especially solar battery - Google Patents

Abstract

The present invention relates to a screen printing apparatus for printing a substrate, particularly a solar cell, comprising at least one printing screen, at least one blade movable along the printing screen, and at least one printing nest, wherein the printing screen And the doctor blade is designed to imprint a conductive adhesive on the substrate.

Description

Screen printing device and substrate printing method for printing flat substrate, especially solar battery

The present invention relates to a screen printing apparatus for printing a planar substrate, particularly a solar cell, comprising at least one printing screen, at least one blade movable along the printing screen, and at least one printing nest. The invention further relates to a method of printing a planar substrate using screen printing techniques.

It is an object of the present invention to improve a screen printing apparatus and a substrate printing method.

To this end, the present invention provides a screen printing apparatus for printing a flat substrate, in particular a solar cell, comprising at least one printing screen, at least one doctor blade movable along the printing screen and a printing nest, wherein the printing net The plate and the blade are designed to imprint a conductive adhesive on the substrate.

Screen printing technology enables high-precision printing directly on substrates, especially solar cells. By applying a conductive adhesive, a connection can be established between the solar cells by means of corresponding connectors (strings). This replaces the welding techniques commonly used in the past. The use of screen printing technology is very advantageous here because it is also possible to print extremely fine structures, so-called bus bars, and to perform extremely gentle operations on substrates, in particular solar cells. If these bus bars are printed, they can replace the bus bars printed by metallization technology.

In a further aspect of the invention, an inversion station for the substrates is provided.

In this way, the screen printing device can print both the top surface of the solar cell and the bottom surface of the solar cell. Thereby, the series contact of the solar cells is achieved in an extremely simple manner, that is, contacting the bottom surface of the solar cell, and then allowing the connecting wires to extend to the top surface of the next solar cell.

In a further aspect of the invention, the screen printing device has at least two printing stations, wherein the first printing station is designed to print the front side of the substrate and the second printing station is designed to print the back side of the substrate.

In a further aspect of the invention, a rotary indexing table is provided, wherein at least one printing nest is disposed on the rotary indexing table and movable from the first printing station to the second printing station.

In a further aspect of the invention, the at least one printing nest has a slot on its placement surface for the substrate, wherein the slots match the areas of the substrate to which the adhesive is to be applied.

Thereby, the printed substrate can be placed on the printing nest with its finished printing side. Thus, the applied adhesive will be located in the slot area of the printing nest without fear of contamination of the printing nest by the adhesive or adhesion of the solar cell to the printing nest.

In a further aspect of the invention, means are provided for at least one-sided lifting of the printing screen during movement of the doctor blade along the printing screen.

With the stencil lifter, a type of adhesive having different rheological properties can be applied to the stencil printing apparatus of the present invention. Depending on the viscosity and other characteristics of the adhesive to be applied, the printing screen is raised during the movement so that it quickly disengages from the applied adhesive as soon as the doctor applies the adhesive to the substrate. The degree of stencil lift is adjusted according to the rheological properties of the type of adhesive used.

Other features and advantages of the invention are set forth in the description of the preferred embodiments of the invention. The individual features shown in the different figures may be combined arbitrarily without departing from the scope of the invention.

10‧‧‧ Screen printing device

12‧‧‧Rotary indexing table

14‧‧‧ arrow

16‧‧‧Printing nest

16A‧‧‧Printing Nest

16B‧‧‧Printing Nest

16C‧‧‧Printing Nest

16D‧‧‧Printing Nest

18‧‧‧ arrow

20‧‧‧ arrow

22‧‧‧ first printing station

24‧‧‧Flip station

26‧‧‧Second printing station

28‧‧‧Solar battery

28A‧‧‧Substrate

28B‧‧‧Substrate

30‧‧‧Printing station

32‧‧‧Printing nest

34‧‧‧ Frame

36‧‧‧Printing stencil

38‧‧‧Scraper

40‧‧‧ arrows, direction of movement

42‧‧‧Rotation point

44‧‧‧ arrow

46‧‧‧孔口

48‧‧‧ slot

50‧‧‧ Screen printing device

52‧‧‧Printing station

54A‧‧‧Solar battery

54B‧‧‧Solar battery

54C‧‧‧Solar battery

54D‧‧‧Solar battery

54E‧‧‧Solar battery

54F‧‧‧Solar battery

54G‧‧‧Solar battery

54H‧‧‧Solar battery

58‧‧‧Transfer and flip station

1 is a schematic plan view of a screen printing apparatus according to a first embodiment of the present invention; FIG. 2 is a side view of the printing station; FIG. 3 is a perspective view of a printing nest of the present invention; A top view of the plate printing device.

The screen printing apparatus of the present invention is for applying a paste-like conductive adhesive to a substrate, particularly a solar cell. These adhesives are used to adhere the battery connector, the so-called string, to the front and back of the solar cell, and then the battery connectors on the solar cells are connected one by one to construct a solar module. This battery connector adhesion method has replaced the welding process that has been used in the past.

- The screen printing apparatus of the present invention directly applies an adhesive to a solar cell by screen printing.

- These adhesives are applied to the front and back of the solar cell simultaneously in one cycle.

- The screen printing unit can be operated in a single task (ie printing only one solar cell per printing process) or in a multi-tasking mode (ie printing two or more solar cells per printing process).

- Multiple solar cells can be printed simultaneously in one cycle through multitasking mode. This can increase the output of printed substrates per hour or reduce the number of printing units required.

- Multi-tasking mode allows the adhesive to be applied to both the front and back sides in one printing process. For example, the front side of the first solar cell is printed with a left stencil layout (Sieblayout), and the back side of the second solar cell is printed with the right stencil layout.

- The sizing layout can be designed separately for the front side of the solar cell.

- The solar cell that has been coated with the effective adhesive surface can be positioned on the printing nest with the adhesive side facing down and further sizing from the top surface.

- Relatively position the adhesive print position on the front side of the solar cell in a precise size with a suitable positioning system.

- The printing station is equipped with an automatic solar cell transfer and turning station. This station is responsible for removing a solar cell that has been printed from one side of the printing nest, and then placing it on the second side of the printing nest without losing the positioning accuracy after flipping.

- There is a rotary indexing table that transfers at least one solar cell with adhesive on both sides to the subsequent process for every 90° rotation.

- All necessary functions are distributed on the four stations on the rotary indexing table, ie the loading position, the printing position, the unloading position and the flipping position. Loading and unloading is accomplished by handling systems and/or conveyor belts.

- Use vacuum to position the solar cell on the printing nest. The printing nests are designed in accordance with the layout and position of the structure to be printed (so-called bus bars) such that the areas of the printed structure remain open in the vacuum holder (ie in the printing nest). It is necessary to print bus bars of different numbers and positions, that is, when printing different structures, the printing nest insert (Drucknesteinlage) can be easily replaced. These printing nests can also be designed for different bus bar spacings, so that it is not necessary to change the printing nest when changing to other bus bar layouts. This allows two, three, four or five bus bars to be printed on the printing station without having to replace the printing nest.

- Due to the intermittent support provided by the printing nest, the risk of solar cell breakage increases, and the risk of fracture can be reduced by adjusting the parameters affecting the risk of fracture, especially the low stencil tension, large stencil and stencil lifting function. The orientation of the bus bars can be either in the printing direction, ie in the direction of the doctor blade, or perpendicular to the printing direction.

- The use of the stencil lifting function of the printing station to process all types of adhesives with different rheological properties on the device.

- The printing station can be loaded or unloaded automatically or manually.

- The printing station can work independently and provide double-sided printed solar cells to subsequent processes.

- The screen printing unit can be used as a stand-alone processing machine or integrated into a total system with different uses.

- The rotary indexing table can be operated in a clockwise or counterclockwise direction.

1 is a schematic plan view of a screen printing apparatus according to a first embodiment of the present invention. The screen printing apparatus 10 has a rotary indexing table 12 that can be rotated 90° each time in a counterclockwise direction as indicated by arrow 14. A plurality of printing nests 16A, 16B, 16C, 16D are provided on the rotary indexing table 12. A loading and unloading station symbolically shown by two arrows 18 and 20 is provided at the 6 o'clock position.

A first printing station 22 containing a first printing screen is provided at the 3 o'clock position. The first printing station is used to imprint a conductive adhesive on the top surface of the solar cell.

A solar cell inversion station 24, shown only schematically, is provided at the 12 o'clock position. The flip station 24 is used to flip and reposition the substrate that has been single-sided printed on the printing station 22 onto the printing nest 16. To this end, the printing nest 16 can be provided with a slot adapted to the position of the bus bar on the solar cell, see FIG. Thereby, it is possible to prevent the printed structure, that is, the bus bar, from adhering to the printing nest 16 due to contact with the surface of the printing nest 16.

A second printing station 26 containing a second printing screen is provided at the 9 o'clock position. The second printing station 26 is used to imprint the conductive adhesive on the back side of the solar cell. After the conductive adhesive is applied to the front side of the solar cell, the printing nest 16 is re-fed to the 6 o'clock position and the substrates 28A, 28B are removed from the printing nest 16A.

2 is a schematic illustration of a printing station 30 for printing solar cells 28 using screen printing techniques. The printing station 30 has a printing nest 32 on which the solar cells 28 lie flat. The frame 34 tensions the printing screen 36. During the printing process, the blade 38 is pressed against the printing screen 36 and the solar cell 28 and then moved to the surface to be printed of the solar cell 28 in the direction indicated by the arrow 40. The doctor blade 38 has a strip of flexible material that is constructed of an elastomeric material and that is angled relative to the printing screen. For the sake of clarity, the blade holder for securing the strip of material is not shown in FIG.

Viewed along the direction of movement 40 of the doctor blade 38 during printing, the front end of the frame 34 is pivotably mounted on the point of rotation 42. Thus, the rear end of the frame 34 can be deflected upwardly in the direction indicated by arrow 44 and can, for example, be moved to the position shown in phantom in Figure 2.

Figure 2 shows the doctor blade 38 in two different positions, wherein the solid line refers to the printing operation At the beginning of the movement, the dashed line refers to the position at which approximately two-thirds of the printing motion on the solar cell 28 is completed. When the doctor blade 38 is in the solid line position, the printing screen 36 is also in a solid line position. The printing screen 36 is in the dashed position when the doctor blade 38 is in its dashed position and the frame 34 is in its raised position as it is reached by the screen lifter. The dotted line only refers to the imaginary position of the printing screen 36 when the frame 34 is in the upwardly deflected position.

When the doctor blade 38 performs a printing motion on the surface of the solar cell 28, the rear end of the frame is raised in the direction indicated by the arrow 44. As a result, in the direction indicated by the arrow 40, the printing screen 36 is more quickly detached from the surface of the solar cell 28 behind the blade. In particular, the release angle of the printed screen section behind the doctor blade 38 and the surface of the solar cell 28 is greater than the situation in which the print screen 36 is not deflected upward during the printing motion of the doctor blade 38 for a given blade position. If the printing screen is not raised, the release angle becomes smaller as the blade stroke increases. In the printing station of the present invention, the purpose of lifting the printing screen 36 in the rear end region is to cause the printing screen 36 to quickly disengage from the surface of the solar cell 28 behind the blade and thereby quickly exit the blade through the printing screen 36 behind the blade 38. An adhesive that is printed on the solar cell 28. Thereby, a precise imprint can be formed during the entire printing movement of the blade 38 on the surface of the solar cell 28, since the printing can be made at the end of the printing movement of the blade 38 by making the release angle higher than a predetermined value or maintaining a constant value. The stencil 36 is quickly detached from the applied adhesive.

3 is a top plan view of the printing nest 32 of FIG. 2. A plurality of apertures 46 are provided in the placement surface of the printing nest 32. The orifice 46 is connected to a vacuum pump not shown. By applying a negative pressure to the orifice 46, the solar cell 28 can be reliably held on the printing nest 32 during printing.

The printing nest 32 further has two slots 48 on its placement surface. The slot 48 matches the structure printed on the solar cell. With the slot 48, the single-sided printed solar cell 28 can be placed on the placement surface of the printing nest 32 with its finished printing side, and the adhesive is applied without contacting the placement surface of the printing nest 32. Thereby, the back side of the solar cell can also be printed without worrying that the solar cell 28 is stuck on the printing nest 32 or that the applied adhesive is damaged or erased.

4 is a schematic view of a screen printing apparatus according to a second preferred embodiment of the present invention. The screen printing apparatus 50 has a rotary indexing table 12 that includes a total of four printing nests 16A, 16B, 16C, and 16D. A printing station 52 including a printing screen is provided at a 12 o'clock position. The printing station 52 is adapted to simultaneously print two solar cells. In Fig. 4, two solar cells 54A and 54B simultaneously printed by the printing station 52 are laid flat on the printing nest 16C. Among them, the solar cell 54A is printed with a conductive adhesive on the back side, and the solar cell 54B is printed with a conductive adhesive on the front side.

The solar cell 54C to be printed is transported to the printing nest 16B at the 3 o'clock position. There is only one solar cell 54C transported to the printing nest 16B at the 3 o'clock position. The solar cell 54D has been placed on the printing nest 16B, which has been printed against the bottom surface of the printing nest 16B.

After the two solar cells 54A, 54B have been printed on the printing station 52, the rotary indexing table 12 is further rotated by 90 in the counterclockwise direction to reach the 9 o'clock position. As shown, a printing nest 16D is placed at the 9 o'clock position, on which two solar cells 54E and 54F are placed. In this two solar cells, only the solar cell 54F is transported away from the printing nest 16D for further processing. The front and back of the solar cell 54F have been printed with an adhesive.

Then, the printing nest 16D is rotated by 90° to move further to the 6 o'clock position. As shown in Fig. 4, a printing nest 16A is provided at the 6 o'clock position. Only one solar cell 54G is placed on the printing nest 16A. The front side of the solar cell 54G has been printed. The solar cell 54G is removed from the printing nest 16A by means of a translating and inverting station 58 which is only schematically shown and repositioned on the printing nest 16A with its top surface facing down in the next cycle, i. On the right side of the display. While the solar cell 54G is being removed, the solar cell 54H that was removed in the previous cycle and turned over therebetween is placed on the right side of the dotted line. Thereafter, the printing nest 16A is further moved counterclockwise to the 3 o'clock position, and as previously described, the unloaded area on the printing nest is occupied by the unprinted solar cell 54C.

The transposition and turning station 58 operates a solar cell with two adsorption units. The first adsorption unit sucks the top surface of the solar cell 54G away from the printing nest 16A and rotates it by 90°. The second adsorber sucks the back surface of the solar cell 54G, receives the solar cell 54G from the first adsorber, and then places the top surface of the solar cell 54G on the placement surface of the printing nest 16A in the next cycle. on.

The transposition and flip station 58 draws a solar cell that is stored during further movement of the rotary indexing table and is repositioned on the printing nest in the next cycle. As a result, there are sometimes two solar cells simultaneously present on the refill and flip station 58. Thereby, the two operations of capturing the first solar cell such as the solar cell 54G and dropping the solar cell of the previous cycle, such as the solar cell 54H, can be simultaneously performed. This measure helps save time and ensures that the solar cell is softened. In particular, the rotary indexing table can be kept for a short cycle time because the first solar cell is taken and the second solar cell system is lowered at the same time, and the handling operation of the solar cell is slow, so that it can be ensured without damage.

Claims (11)

A screen printing apparatus for printing a flat substrate, in particular a solar cell, comprising at least one printing screen, at least one blade movable along the printing screen, and at least one printing nest, wherein the printing screen and the blade design It is used to apply a conductive adhesive to the substrate in the form of a very fine structure, a so-called bus bar, for the connection between the two planar substrates, the so-called string application. A screen printing apparatus according to claim 1, wherein an inversion station for the substrates is provided. A screen printing apparatus according to claim 1 or 2, wherein the screen printing apparatus has two printing stations, wherein the first printing station is designed to print the front side of the substrate, and the second printing station is designed to print the back side of the substrate. The stencil printing apparatus according to claim 1 or 2, wherein a rotary indexing table is provided, wherein at least one printing nest is movable from the first printing station to the second printing station on the rotary indexing table . The screen printing apparatus according to claim 1 or 2, wherein the at least one printing nest has a slot on a surface on which the substrate is applied, wherein the slots are opposite to the areas of the substrate to which the adhesive is to be printed. adaptation. A screen printing apparatus according to the above claim 1 or 2, wherein means for raising at least one side of the printing screen during the movement of the blade during printing is provided. A screen printing apparatus according to claim 3, wherein a rotary indexing table is provided, wherein at least one printing nest is movable from the first printing station to the second printing station on the rotary indexing table. The stencil printing apparatus of claim 3, wherein the at least one printing nest has a slot on a placement surface for the substrate, wherein the slots are adapted to the areas of the substrate to which the adhesive is to be applied . A screen printing apparatus according to the above claim 3, wherein means for raising the printing screen at least one side during the movement of the blade during printing is provided. A method of printing a substrate, in particular a solar cell, using a screen printing device according to any one of claims 1 to 9, wherein the conductive adhesive is applied to the two planar substrates in the form of a very fine structure, a so-called bus bar. The connector between the two planar substrates is a so-called string application. The method of claim 10, wherein the strings are applied to the bus bars printed on the two planar substrates to thereby connect the two planar substrates.