CN215266317U - Solar cell, tile-overlapping assembly and printing screen - Google Patents

Abstract

The utility model provides a solar wafer, including at least having a main grid line and with the front of the vice grid line of a plurality of interval arrangements that the main grid line was established perpendicularly, its characterized in that still includes: and the back field is provided with a plurality of thin grid lines which are parallel to the secondary grid lines and are arranged at intervals. The utility model discloses still be equipped with the two-sided shingle assembly that has this battery piece structure and be used for printing the printing half tone of this battery piece back of the body field structure. The back surface field structure of the utility model adopts the aluminum paste full back surface covering arrangement in the existing back surface field to be replaced by the thin grid line formed by the aluminum paste, the output power of the battery component can be improved while the usage amount of the aluminum paste in the back surface field is reduced, the conversion efficiency of the laminated tile component can reach 24.48 percent to the maximum, and the optimal thin grid line interval and the optimal line width size are provided; and the warping degree of the battery piece after the back field sintering can be kept within the range of 1.1-1.3 mm.

Description

Solar cell, tile-overlapping assembly and printing screen

Technical Field

The utility model belongs to the technical field of solar cell stack tile subassembly production, especially, relate to a solar wafer, stack tile subassembly and printing half tone.

Background

The conventional cell is used for generating power on the front side, and the back side is covered by aluminum paste in a full-size mode, so that the generated energy is low, the consumption of raw materials of the aluminum paste is large, and the gain of power is lost due to the consumption of the aluminum paste. Particularly, with the development of large-sized silicon wafers, large-sized cells are gradually applied to solar energy laminated modules, and the consumption of aluminum paste required for full coverage of a back field in a single cell is further increased, so that the power gain is extremely low, the conversion efficiency of the large-sized cells cannot be maximized, and the stability of the front power of the cells is also influenced. And the aluminum paste layer which is excessively covered causes the bending deformation of the battery piece after sintering, seriously influences the cutting and slicing of the battery piece and is easy to crack.

SUMMERY OF THE UTILITY MODEL

The utility model provides a solar wafer, imbricate subassembly and printing half tone, especially be applicable to the back of the body field structure of two-sided battery piece, solve among the prior art battery piece power low, conversion efficiency low, the little and yielding technical problem of power increase.

In order to solve the technical problem, the utility model discloses a technical scheme is:

a solar cell piece comprises at least one main grid line and the front surface of a plurality of auxiliary grid lines which are arranged at intervals and are vertical to the main grid line, and further comprises:

and the back field is provided with a plurality of thin grid lines which are parallel to the secondary grid lines and are arranged at intervals.

Furthermore, the thin grid lines are uniformly distributed on the back surface field;

preferably, the line distance between adjacent thin grid lines is 0.9-1.1 mm;

preferably, the width of the fine gate line is 150-180 μm;

preferably, the line distance between adjacent thin grid lines is 1 mm.

Furthermore, at least one back electrode groove perpendicular to the thin grid line is arranged in the back field;

the back pole grooves are uniformly arranged in the length direction of the back field in a penetrating manner;

the back pole points of all the battery pieces are arranged in the back pole groove and are arranged in a single-row staggered mode along the length direction of the back pole groove.

Further, the width of the back pole groove is 4-6 mm;

preferably, the number of the back electrode grooves is 1-5;

preferably, the back electrode groove and the main grid line are arranged in a non-overlapping mode.

Furthermore, a plurality of rows of pad grooves which are arranged at intervals are arranged in the back surface field along the length direction of the thin grid line;

preferably, a group of pad grooves is symmetrically arranged on two sides of each back electrode groove;

preferably, pad points of the battery pieces are arranged in the pad grooves and are arranged in one-to-one correspondence with the pad grooves.

Further, the back electrode groove and the pad groove are both silver paste printing structures;

the back pole point and the pad point are both structures printed by aluminum paste.

A tile-stacking assembly comprises a plurality of groups of battery strings which are vertically arranged and are formed by connecting battery sheets in a tile-stacking mode, and the number of the battery strings is five.

A screen printing plate is used for screen printing of the back field of the battery piece and at least comprises a screen printing plate, wherein the screen printing plate at least is provided with a plurality of thin grid lines which are parallel to the secondary grid lines and are arranged at intervals.

Further, the screen printing plate I is also provided with:

at least one back electrode groove perpendicular to the thin grid line; and

a plurality of rows of pad grooves arranged at intervals are arranged along the length direction of the thin grid line;

the back electrode grooves penetrate through the first screen printing plate in the length direction and are uniformly arranged;

the back pole points of all the battery pieces are arranged in the back pole groove and are arranged in a single-row staggered manner along the length direction of the back pole groove;

the fine grid lines are uniformly distributed on the first screen printing plate;

the line distance between the adjacent thin grid lines is 0.9-1.1 mm;

the width of the thin grid line is 150-180 mu m;

preferably, the line distance between adjacent thin grid lines is 1mm

The back electrode groove and the main grid line are arranged in a non-overlapping mode;

the width of the back pole groove is 4-6 mm;

the number of the back electrode grooves is 1-5;

and a group of pad grooves are symmetrically arranged on two sides of each back electrode groove.

Further, the method also comprises the following steps: the printing screen is used for printing a back pole point arranged on the inner side of the back pole groove and a pad point II screen arranged on the inner side of the pad groove; the external dimensions of the second screen printing plate and the first screen printing plate are the same as the back surface field dimension;

all the back pole points are arranged in the back pole groove and are arranged in a single-row staggered manner along the length direction of the back pole groove;

the pad points are arranged in the pad grooves and are arranged in one-to-one correspondence with the pad grooves.

Compared with the prior art, the utility model discloses a pair of solar wafer adopts and gets rid of the structure that the whole back of aluminium thick liquid covers the setting in the current back of the body field, changes the thin grid line that the aluminium thick liquid formed into and replaces, when reducing the aluminium thick liquid quantity in the back of the body field, still can improve battery pack's output, can make the conversion efficiency of shingle assembly the highest 24.48% that can reach to propose best thin grid line interval and line width size. And the warping degree of the battery piece after the back field sintering can be kept within the range of 1.1-1.3 mm.

The utility model discloses still be equipped with the two-sided shingle assembly that has this battery piece structure and be used for printing the printing half tone of this battery piece back of the body field structure.

Drawings

Fig. 1 is a schematic structural diagram of a solar cell back surface field according to a first embodiment of the present invention;

FIG. 2 is an enlarged view of portion A of FIG. 1;

fig. 3 is a schematic structural diagram of a solar cell back surface field according to a second embodiment of the present invention;

fig. 4 is a schematic structural diagram of a solar cell back surface field according to a third embodiment of the present invention;

fig. 5 is a schematic circuit diagram of a shingle assembly according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a first screen printing plate according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a second screen printing plate according to an embodiment of the present invention.

In the figure:

10. back surface field 11, thin grid line 12 and back surface electrode groove

13. pad groove 14, back pole point 15 and pad point

16. Positioning point 17, positioning groove 20 and first screen printing plate

21. Mark point 30 and second screen printing plate

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

This embodiment provides a solar cell, as shown in fig. 1, a solar cell includes a front surface having at least one main gate line and a plurality of auxiliary gate lines arranged at intervals and perpendicular to the main gate line, and further includes: a back field 10 having a plurality of thin gate lines 11 arranged in parallel with and spaced apart from the sub-gate lines. The main grid lines and the auxiliary grid lines in the front face are formed by silver paste, and the main grid lines mainly collect and conduct current from the auxiliary grid lines. The thin grid lines 11 formed by the aluminum paste in the back field 10 are used for collecting matrix charges and are used as reflection fields of reflected electrons, so that the conversion efficiency of the battery is improved; the excessive aluminum paste area can influence the current circulation, increase the resistance and reduce the gain effect of the front power of the battery; but also results in severe bending and unacceptable warpage during subsequent sintering. Therefore, the structure of the aluminum paste grid line is adopted to replace the structure covered by the existing full back surface field aluminum paste, so that the resistance of the electronic load is reduced, and the conversion efficiency of the front surface of the battery is improved; meanwhile, a small amount of thin grid lines 11 which are uniformly arranged are more favorable for solidification of sintering, stress concentration caused by aggregation and reunion of aluminum paste is reduced, the thin grid lines 11 which are arranged in parallel are equivalent to a plurality of stress release grooves which are separately arranged, stress can be quickly released, and therefore concentration of stress after sintering can be reduced, deformation of the thin grid lines is reduced, and the warping degree of the battery piece is stable and qualified. The usage amount of the aluminum paste can be reduced, and the production cost is reduced. In addition, the thin grid lines 11 arranged in parallel with the secondary grid lines are beneficial to current transmission, and current disconnection of the battery pieces stacked up and down is prevented.

Furthermore, at least one back electrode groove 12 perpendicular to the thin gate lines 11 and used for setting a back electrode 14 is also arranged in the back field 10, and the back electrode grooves 12 are uniformly arranged in the length direction penetrating through the back field 10. The back pole 14 is a structure formed by silver paste, and the back pole 14 of all the battery pieces is wrapped by the back pole groove 12 formed by aluminum paste, and is arranged in a single-row staggered manner along the length direction of the back pole groove 12, as shown in fig. 2. The back pole 14 is used for collecting current from the thin grid lines 11, the current is transmitted and collected through conductive adhesive or welding rods connected with the back pole 14 in a welding mode, and then the current is led out through the welding rods, and the back field 10 can also collect current-carrying electronic charges and collect the current together to lead out the current as the front surface, so that the overall power of the battery piece can be increased, and meanwhile, the power of the front surface of the battery piece cannot be reduced due to the increase of series resistance.

Further, the thin gate lines 11 are uniformly distributed on the back surface field 10. Preferably, according to the limitation of the resistance of the cell, when the line distance between the adjacent thin grid lines 11 is 0.9-1.1mm, the conversion efficiency of the obtained cell is the highest; if the line distance between adjacent thin gate lines 11 is too wide, the number of thin gate lines 11 per unit area decreases, the transmission resistance increases, and the warpage decreases.

The battery pieces of the back field 10 with different line distances of the thin grid lines 11 are subjected to high-temperature sintering by the same process method, and the warping degrees of the obtained battery pieces are shown in table 1, and as can be seen from table 1, the warping degrees are gradually reduced along with the increase of the line distances of the thin grid lines 11, so that the deformation amount is gradually reduced. Compared with the back surface field 10 structure covered by the full back surface aluminum paste, the structure provided by the embodiment not only reduces the usage of the aluminum paste, but also can reduce the deformation of the battery piece to the maximum extent, so as to obtain the battery piece with the back surface field 10 structure, the warping degree of which is stable and qualified.

TABLE 1 Back surface field of different fine grid lines, degree of warp of the obtained battery piece

During the processing, the laser grooving line must match with the width of the aluminum paste fine grid line 11, and preferably, the width of the fine grid line 11 is 150-. This is because, if the width of the fine grid line 11 is less than 150 μm, the transmission resistance is too large, which is not favorable for outputting the battery power, and the precision of the laser cannot be achieved at present; if the width of the thin gate line 11 is greater than 180 μm, the production cost is too high, and the production efficiency is too low.

Further, as shown in fig. 2, the width W1 of the back pole groove 12 is 4-6mm, and preferably, the number of the back pole grooves 12 is 1-5, so that the number of the back pole grooves 12 is the number of the back pole points 14 arranged, i.e. how many back pole points 14 are arranged in the back field 10 of each cell. If the number of the back electrode grooves 12 is greater than 5, the number of the battery strips obtained after cutting the battery piece is larger, but the width of the battery strips is narrower, so that the stacking height of the laminated tile assembly is too high and the laminated tile assembly is not suitable for a power station. Further, the number of the back pole grooves 12 is 1-5, preferably 3, and the distribution structure is shown in fig. 1, fig. 3 and fig. 4, respectively, that is, when the number of the back pole grooves 12 is 3, the structure is shown in fig. 1; when the number of the back pole grooves 12 is 1, the structure is shown in FIG. 3; when the number of the back pole grooves 12 is 5, the structure is shown in fig. 4. And the back electrode grooves 12 and the main grid lines (omitted in the drawing) in the front surface are arranged in a non-overlapping mode, so that the back electrode grooves 12 do not influence the collection of the current on the main grid lines on the front surface of the battery piece. Of course, the structure of the back pole groove 12 with other values in the back field 10 can be omitted here, but it is within the scope of the present disclosure.

Furthermore, a plurality of rows of pad grooves 13 which are arranged at intervals and independently are arranged in the back field 10 along the length direction of the thin grid lines 11; namely, three rows of pad slots 13 are arranged in the back surface field 10, each row has a plurality of independent and spaced pad slots 13, and two sides of each back electrode slot 12 are symmetrically provided with a group of pad slots 13. Preferably, the pad points 15 of the battery piece are arranged in the pad grooves 13, as shown in fig. 5, and the pad points 15 are arranged in one-to-one correspondence with the pad grooves 13.

Preferably, as shown in FIG. 2, the width W2 of the pad slot 13 is 4-6mm, the length H thereof is 8-10mm, and all the pad points 15 are arranged in the pad slot 13 and wrapped by the aluminum paste in the pad slot 13.

In this embodiment, the back electrode slot 12 and the pad slot 13 are both silver paste printed structures; the back pole 14 and the pad point 15 are the same as the fine grid line 11 and are both of the structure printed by aluminum paste. The outer circles of all back pole points 14 to the outer width edges of the back pole grooves 12 are all provided with certain gaps, and the outer circles of all pad points 15 to the outer edges of the pad grooves 13 are all provided with certain gaps; that is, the back pole 14 and the pad point 15 formed by the silver paste are respectively wrapped by the back pole groove 12 and the pad groove 13 arranged by the aluminum paste; the battery piece formed by the structure not only facilitates the collection and extraction of current, but also ensures that the front power of the battery piece is not reduced due to the increase of the series resistance.

Furthermore, a plurality of positioning points 16 for subsequent equal cutting and positioning are further arranged on the back surface field 10, the positioning points 16 are respectively arranged along the periphery of the back surface field 10, and positioning grooves 17 are arranged around the positioning points 16, so that the silver paste positioning points 16 are wrapped by the aluminum paste positioning grooves 17. In this embodiment, six positioning points 16 are provided, and two and one positioning points 16 are respectively provided on two sides from left to right along the length direction of the thin gate line 11; two positioning points 16 are respectively arranged on two sides from top to bottom along the length direction of the back pole groove 12, and all the positioning points 16 are arranged in the area where the thin grid line 11 is located, so that the welding of the back pole point 14 and the pad point 15 is prevented from being influenced.

A circuit structure diagram of a laminated assembly is shown in fig. 5, and the laminated assembly comprises a plurality of groups of battery strings which are vertically arranged and are formed by connecting battery sheets in a laminated manner, wherein the number of the battery strings is five. In this embodiment, the size of the battery piece is 192mm, 200mm, or 210mm, if a commonly used battery piece is adopted, that is, after the battery pieces with the side length less than 192mm are equally divided into 1/2 or 1/3, the equally divided battery pieces are formed into battery strings, and 6 battery strings are arranged side by side, the finally formed assembly width reaches 1200 and 1500mm, which is seriously beyond the standard range of 992 and 1050mm of the existing production assembly width, and thus mass production cannot be performed, and the utilization rate of the battery piece is very low.

Therefore, for the battery piece made of the large-size silicon wafer with the side length of 192mm or 200mm or 210mm, when the back field 10 structure of the battery piece is ensured as described above, the sliced battery pieces obtained by dividing the battery piece into 5 equal parts, 6 equal parts, 7 equal parts or 8 equal parts are connected in series to form 5 strings of battery strings, and then the 5 strings of battery strings are connected in parallel to form a tile assembly, so that the width dimension of the tile assembly can be controlled within the range of 1048 and 1098mm, and the tile assembly with the width does not exceed the limit of each production device of the existing assembly line, thereby realizing assembly line compatibility and mass production, and simultaneously realizing the matching with auxiliary material mass production processes such as assembly glass, a back plate, a frame and the like, transportation, a power station end bracket and the like which are commonly used in the industry.

Further, for the battery pieces of the back surface field 10 with different line distances of the fine grid lines 11, 8 equal divisions are performed to obtain sliced battery pieces, the sliced battery pieces of 1/8 are connected in series to form battery strings, 5 battery strings with the same structure are connected in parallel to be connected in a tiling mode to form different tiling components, and under the condition that other processes are not changed, finally obtained battery resistances and conversion efficiencies are respectively shown in table 2. As can be seen from table 2, when the pitch of the thin gate lines 11 is gradually increased from 0.8mm to 1mm, the conversion efficiency is gradually increased, and particularly, when the pitch is 1mm, the conversion efficiency is at most 21.42%; when the thickness is gradually increased from 1mm to 1.3mm, the conversion efficiency of the laminated assembly is gradually reduced; from this set of data, it can be seen that the conversion efficiencies obtained are all higher than 21.3% and within 21.38-21.48% when the line spacing is 0.9-1.1 mm.

TABLE 2 Back surface field of line spacing of different fine grid lines, resistance and conversion efficiency of the resulting shingle assembly

A printing screen is used for carrying out screen printing on a back field 10 of a battery piece, and comprises a first screen 20 and a second screen 30 as shown in figures 6 and 7, wherein the first screen 20 at least comprises a plurality of fine grid lines 11 which are parallel to and spaced from the secondary grid lines in the front surface, the overall dimensions of the second screen 30 and the first screen 20 are the same as the overall dimension of the back field 10, and the structure of the back field 10 can be obtained after the second screen 30 and the first screen 20 are overlapped.

Specifically, the fine grid lines 11 are uniformly distributed on the first screen 20; and the line distance between the adjacent thin grid lines 11 is 0.9-1.1 mm; and the width of the fine gate line 11 is 150-. Preferably, the line distance between adjacent thin gate lines 11 is 1 mm.

Further, as shown in fig. 6, at least one back electrode slot 12 perpendicular to the thin grid line 11 and a plurality of rows of pad slots 13 spaced apart from each other along the length direction of the thin grid line 11 are disposed on the first screen 20. Wherein, the back pole slots 12 are uniformly arranged in the length direction of the first screen 20; and the back electrode groove 12 and the main grid line are not overlapped.

Preferably, the width of the back pole groove 12 is 4-6 mm; and the number of the back pole grooves 12 is 1-5. In the present embodiment, the number of the back electrode grooves 12 is selected to be three; and there are three rows of pad slots 13. And a group of pad grooves 13 are symmetrically arranged on both sides of each back pole groove 12.

Further, as shown in fig. 7, the second screen 30 is used for printing the back pole points 14 disposed inside the back pole grooves 12, the pad points 15 disposed inside the pad grooves 13, and the positioning points 16 for cutting and positioning.

All the back pole points 14 are arranged in the back pole groove 12 and are arranged in a single-row staggered manner along the length direction of the back pole groove 12. The pad points 15 are arranged in the pad grooves 13 and are arranged in one-to-one correspondence with the pad grooves 13. And the location points 16 are placed in the location slots 17.

In the work, firstly, the second screen printing plate 30 is used for silver paste printing, namely, the back pole 14, the pad point 15 and the positioning point 16 formed by all silver pastes at the printing position are firstly printed, and in the first printing, the overlapping arrangement of the identification mark point 21 and the silicon chip does not need to be arranged on the second screen printing plate 30.

And then, performing aluminum paste printing by using the first screen printing plate 20, and printing the fine grid line 11, the back electrode groove 12, the pad groove 13 and the positioning groove 17 for wrapping the positioning point 16 by using aluminum paste, so as to obtain the aluminum paste fine grid line 11, the back electrode point 14 wrapped by the aluminum paste, the pad point 15 and the positioning point 16. Because the precision of the back surface field 10 needs to be ensured in the secondary printing, four mark points 21 are further arranged on the first screen 20 and are respectively arranged at the end parts of two sides of two back electrode grooves 12 at the outermost sides of the back electrode grooves 12.

The separately arranged screen printing plate structures can respectively obtain a back pole 14, pad points 15 and positioning points 16 formed by silver paste; and the thin grid line 11, the back electrode groove 12, the pad groove 13 and the positioning groove 17 are formed by aluminum paste, and the back electrode point 14 and the pad point 15 are completely and respectively wrapped in the back electrode groove 12 and the pad groove 13 formed by the aluminum paste. The printing structure is simple, the printing precision is high, and the structure of the battery piece back surface field 10 which has stable quality, high conversion efficiency and difficult deformation can be obtained.

Adopt the utility model discloses a solar wafer adopts and gets rid of the structure that the full back of aluminium thick liquid covered the setting in the current back of the body field, changes the thin grid line that the aluminium thick liquid formed into and replaces, when reducing aluminium thick liquid quantity in the back of the body field, still can improve battery pack's output, can make the conversion efficiency of shingle assembly the highest 24.48% that can reach to propose best thin grid line interval and line width size. And the warping degree of the battery piece after the back field sintering can be kept within the range of 1.1-1.3 mm. The utility model discloses still be equipped with the two-sided shingle assembly that has this battery piece structure and be used for printing the printing half tone of this battery piece back of the body field structure.

The embodiments of the present invention have been described in detail, and the description is only for the preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. All the equivalent changes and improvements made according to the application scope of the present invention should still fall within the patent coverage of the present invention.

Claims (12)

1. A solar cell piece comprises at least one main grid line and a plurality of auxiliary grid lines which are arranged at intervals and are perpendicular to the main grid line, and is characterized by further comprising:

and the back field is provided with a plurality of thin grid lines which are parallel to the secondary grid lines and are arranged at intervals.

2. The solar cell of claim 1, wherein the fine grid lines are uniformly distributed on the back surface field;

the line distance between the adjacent thin grid lines is 0.9-1.1 mm;

the width of the thin gate line is 150-180 mu m.

3. The solar cell sheet according to claim 2, wherein the line distance between adjacent thin grid lines is 1 mm.

4. The solar cell sheet according to any one of claims 1 to 3, wherein at least one back electrode groove perpendicular to the thin grid line is further disposed in the back surface field;

the back pole grooves are uniformly arranged in the length direction of the back field in a penetrating manner;

the back pole points of all the battery pieces are arranged in the back pole groove and are arranged in a single-row staggered mode along the length direction of the back pole groove.

5. The solar cell piece according to claim 4, wherein the back electrode groove width is 4-6 mm;

the number of the back electrode grooves is 1-5;

the back electrode groove and the main grid line are arranged in a non-overlapping mode.

6. The solar cell as claimed in claim 5, wherein a plurality of rows of pad slots are arranged in the back surface field at intervals along the length direction of the thin grid line;

a group of pad grooves is symmetrically arranged on two sides of each back electrode groove;

pad points of the battery pieces are arranged in the pad grooves and are arranged in one-to-one correspondence with the pad grooves.

7. The solar cell of claim 6, wherein the back electrode groove and the pad groove are both silver paste printed structures;

the back pole point and the pad point are both structures printed by aluminum paste.

8. A stack assembly comprising a plurality of battery strings arranged in vertical rows and connected in a stacked manner using the battery sheets according to any one of claims 1 to 7, wherein the number of the battery strings is five.

9. A screen printing plate is used for screen printing the back field of the battery piece according to any one of claims 1 to 7, and is characterized by comprising at least one screen printing plate, wherein the screen printing plate at least comprises a plurality of fine grid lines which are parallel to the secondary grid lines and are arranged at intervals.

10. The printing screen of claim 9, wherein the first screen is further provided with:

at least one back electrode groove perpendicular to the thin grid line; and

a plurality of rows of pad grooves arranged at intervals are arranged along the length direction of the thin grid line;

the back electrode grooves penetrate through the first screen printing plate in the length direction and are uniformly arranged;

the back pole points of all the battery pieces are arranged in the back pole groove and are arranged in a single-row staggered manner along the length direction of the back pole groove;

the fine grid lines are uniformly distributed on the first screen printing plate;

the line distance between the adjacent thin grid lines is 0.9-1.1 mm;

the width of the thin gate line is 150-180 mu m.

11. The printing screen of claim 10, wherein the line spacing between adjacent fine grid lines is 1 mm;

the back electrode groove and the main grid line are arranged in a non-overlapping mode;

the width of the back pole groove is 4-6 mm;

the number of the back electrode grooves is 1-5;

and a group of pad grooves are symmetrically arranged on two sides of each back electrode groove.

12. A printing screen according to claim 10 or 11, further comprising: the printing screen is used for printing a back pole point arranged on the inner side of the back pole groove and a pad point II screen arranged on the inner side of the pad groove; the external dimensions of the second screen printing plate and the first screen printing plate are the same as the back surface field dimension;

all the back pole points are arranged in the back pole groove and are arranged in a single-row staggered manner along the length direction of the back pole groove;

the pad points are arranged in the pad grooves and are arranged in one-to-one correspondence with the pad grooves.

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