JP7377671B2 - How to expand the sheet - Google Patents

Description

The present invention relates to a method of expanding a sheet to which a work is attached.

BACKGROUND ART Conventionally, a method is known in which a modified layer is formed on a workpiece by laser beam irradiation, and then a sheet to which the workpiece is attached is expanded using a sheet expansion device, thereby dividing the workpiece. A specific configuration of the seat expansion device is known, for example, as disclosed in Patent Document 1.

Patent Document 1 discloses that by expanding the four sides of a sheet to which a workpiece is attached while being held by a holding mechanism, the sheet can be expanded so that the distance between the chips is appropriate even when the chips have different sizes in the vertical and horizontal directions. An expansion device is disclosed that can expand the .

Japanese Patent Application Publication No. 2014-143297

As disclosed in Patent Document 1, in a configuration in which a sheet is held between upper and lower holding units, depending on the type of sheet, slippage may occur between the holding unit and the sheet when expanding, and the sheet may not be expanded sufficiently. , there is a concern that poor division may occur.

In particular, as disclosed in Patent Document 1, in a configuration in which a sheet is held between upper and lower rollers, the contact area between the rollers and the sheet is limited, making it easy to slip. A special challenge is to create a configuration that is suitable for

In view of the above problems, the present invention proposes a new technique for suppressing the phenomenon of sheet slipping when expanding the sheet.

According to one aspect of the present invention,
A method of expanding a sheet to which a work is attached, the method comprising:
A clamping mechanism including a pair of first direction clamping means facing each other in a first direction, and a pair of second direction clamping means facing each other in a second direction orthogonal to the first direction,
The pair of first direction clamping means each have an upper clamping part and a lower clamping part, and a plurality of rollers rotating around a rotation axis parallel to the first direction are provided at the lower part of the upper clamping part. is arranged, a plurality of rollers are arranged above the lower holding part and rotate around a rotation axis parallel to the first direction,
The pair of second direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of screws rotating around a rotation axis parallel to the second direction. a preparation step of preparing an expansion device in which a roller is disposed, and a plurality of rollers are disposed above the lower holding part and rotate around a rotation axis parallel to the second direction;
a clamping step of clamping a portion of the sheet located outside the work with the plurality of rollers of the clamping mechanism;
an expansion step of expanding the sheet by moving the pair of first direction clamping means in a direction away from each other and moving the pair of second direction clamping means in a direction away from each other;
It is assumed that at least one of the roller of the expansion device and the pinched portion of the sheet that is pinched by the roller of the pinching mechanism is subjected to a non-slip finish.

According to the configuration of the present invention, the occurrence of slippage between the rollers is suppressed, and the occurrence of areas that cannot be sufficiently expanded and are not divided into chips, or the formation of sufficient intervals between chips is suppressed. It is possible to reduce the risk of the chips coming into contact with each other during subsequent handling and damaging the chips.

FIG. 2 is a diagram showing a workpiece as a workpiece and a sheet to which the workpiece is attached. FIG. 3 is a diagram illustrating a configuration example of an expansion device. FIG. 6 is a diagram illustrating an example of applying anti-slip processing to a roller. FIG. 6 is a diagram illustrating an example of applying anti-slip processing to the back surface of a sheet. (A) is a plan view showing the clamping step. (B) is a side view showing the clamping step. (A) is a plan view showing an expansion step. (B) is a side view showing the expansion step.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
<Works and sheets>
FIG. 1 is a diagram showing a workpiece 10 as a workpiece and a sheet 1 to which the workpiece 10 is attached.
The workpiece 10 is, for example, a disk-shaped wafer such as a semiconductor wafer or an optical device wafer. On the surface of the workpiece 10, a plurality of dividing lines 101 that intersect each other at right angles are set in a grid pattern.

For example, before or after the workpiece 10 is pasted onto the sheet 1, a dividing starting point is formed along the dividing line 101. Then, with the workpiece 10 on which the division starting point has been formed adhered to the sheet 1, the sheet 1 is expanded and divided into chips along the division starting point.

In addition to the modified layer formed in the workpiece 10 by laser beam irradiation, the division starting point formed along the division line 101 is formed by forming a groove on the surface of the workpiece 10 along the division line 101, and forming the groove. It can also be used as a starting point for division. The grooves can be formed, for example, by ablation processing using laser irradiation, cutting processing using a cutting blade, or groove processing such as scribing.

The sheet 1 has an adhesive layer 12 to which a workpiece 10 is attached on one side of a base material 11 made of a synthetic resin sheet having expandability such as polyvinyl chloride or polyolefin. A large rectangular (quadrangular) one is also used.

The workpiece 10 to be processed may be a wafer such as a semiconductor wafer or the like, as well as DBG (Dicing Before Grinding), in which half-cut grooves are formed on the surface of the workpiece along the dividing line with a blade, and then the workpiece is divided by back grinding. A chip mounting plate attached to a wafer that has been divided into chips by SDBG (Stealth Dicing Before Grinding: a process in which the back side of the workpiece is divided by grinding after performing SD processing (STEALTH DICING: registered trademark)). Targets include adhesive sheets such as DAF (Die Attach Film), and various plate-like materials such as glass, ceramics, and resin.

<Expansion device>
Next, as shown in FIG. 2, an embodiment of an expansion device for expanding a sheet to which a work is attached will be described. This expansion device 2 includes a fixed base 20 in the shape of a square with four corners formed at right angles, and a circular shape arranged on the fixed base 20 on which a sheet with a workpiece pasted is placed horizontally. A plate-shaped holding table 3, a first holding means 4A, a second holding means 4B, a third holding means 4C, a fourth holding means 4D that hold a sheet (not shown) placed on the holding table 3, and these holding means. A first moving means 5A, a second moving means 5B, and a third and fourth holding means 4C to 4D are provided for each of the means 4A to 4D and move the first and second holding means 4A to 4B in the first direction, respectively. A third moving means 5C and a fourth moving means 5D are provided, which respectively move the two in the second direction.

The holding table 3 is supported on the upper surface of the central portion of the fixed base 20 via a cylindrical table 30. The holding table 3 is rotatably supported on the cylindrical table 30 by a rotation mechanism (not shown) and movable up and down on the cylindrical table 30 by a vertical movement mechanism (not shown). The upper surface of the holding table 3 has a diameter that allows the workpiece to be placed on it, and the sheet with the workpiece attached is placed on the upper surface of the holding table 3 with the workpiece on top and arranged concentrically. It will be placed.

At the center of each of the four edges 200a, 200b, 200c, and 200d of the fixed base 20, a rectangular protrusion 201 that protrudes outward is formed, respectively. A first rectangular guide groove 201a and a second rectangular guide groove 201a extending along the direction in which the corresponding convex part 201 extends are provided in a portion of the fixed base 20 extending from each convex part 201 to the inside of the convex part 201 (toward the holding table 3 side). A guide groove 201b, a third guide groove 201c, and a fourth guide groove 201d are formed, respectively.

As shown in FIG. 2, in this case, the extending direction of the pair of mutually parallel end edges 200c and 200d of the fixed base 20 is the first direction, the direction perpendicular to the first direction, and the extending direction of the end edges 200a and 200b is the first direction. A first clamping means 4A and a second clamping means 4B are respectively disposed at both ends of the fixed base 20 in the first direction, and a third clamping means 4C and a fourth clamping means are disposed at both ends of the fixed base 20 in the second direction. A clamping means 4D is provided respectively.

The first moving means 5A and the second moving means 5B reciprocate the first holding means 4A and the second holding means 4B along the first direction, and the third moving means 5C and the fourth moving means 5D reciprocate the first holding means 4A and the second holding means 4B, respectively. The third clamping means 4C and the fourth clamping means 4D are each moved back and forth along the second direction.

The first clamping means 4A and the second clamping means 4B face each other across the holding table 3 in the first direction, and are arranged to be movable in the first direction with respect to the first guide groove 201a and the second guide groove 201b, respectively. has been done. Further, the third holding means 4C and the fourth holding means 4D face each other across the holding table 3 in the second direction, and are movable in the second direction with respect to the third guide groove 201c and the fourth guide groove 201d, respectively. It is arranged.

The first to fourth holding means 4A to 4D have the same configuration, and include an L-shaped movable base 41 that is movably incorporated along the guide grooves 201a to 201d, and a vertically movable base 41 inside the movable base 41. It is provided with a lower clamping mechanism 42 and an upper clamping mechanism 43 that can be attached, and a lower moving mechanism 44 and an upper moving mechanism 45 that move these clamping mechanisms 42 and 43 in the vertical direction, respectively.

The movable base 41 includes a slide portion 411 that is slidably fitted into each of the guide grooves 201a to 201d, and a support portion 412 that is erected at the outer end of the slide portion 411.

A guide rail 412a extending in the vertical direction is formed on the inner surface of the support portion 412. Furthermore, a guide groove 412b extending in the vertical direction is formed on the outer surface of the support portion 412. Furthermore, a guide hole 412c is formed in the support portion 412 and extends in the vertical direction from the inner surface of the guide rail 412a to the guide groove 412b.

The first to fourth moving means 5A to 5D that move the first to fourth holding means 4A to 4D along the guide grooves 201a to 201d, respectively, have the same configuration, are screwed into the slide portion 411, and are screwed into the guide grooves 201a to 201d. It has threaded rods 51 each extending along 201d, and a pulse motor 52 that is disposed on the convex portion 201 and drives the threaded rods 51 in forward and reverse rotation. The tips of the threaded rods 51 are rotatably supported by bearings 53 fixed inside the guide grooves 201a to 201d on the fixed base 20, respectively.

The slide portion 411 of the movable base 41 to which the threaded rod 51 is screwed rotates from the outside to the inside or from the inside to the outside along the guide grooves 201a to 201d depending on the rotational direction of the threaded rod 51 that is rotationally driven by the pulse motor 52. As a result, the first and second clamping means 4A, 4B are reciprocated in the first direction, and the third and fourth clamping means 4C, 4D are reciprocated in the second direction. Therefore, the first moving means 5A and the second moving means 5B are capable of moving the first holding means 4A and the second holding means 4B in directions away from each other in the first direction. The fourth moving means 5D allows the third holding means 4C and the fourth holding means 4D to move in directions away from each other in the second direction.

The lower clamping mechanism 42 includes an arm part 421 that is supported to be vertically movable along a guide rail 412a and extends inward, and a lower clamping part fixed to the tip of the arm part 421 perpendicularly to the arm part 421. 422, and is configured in a substantially T-shape. A base end portion 421c of the arm portion 421 passes through the guide hole 412c and is disposed within the outer guide groove 412b.

The lower clamping parts 422 of the first and second clamping means 4A, 4B extend parallel to the second direction, and the lower clamping parts 422 of the third and fourth clamping means 4C, 4D extend parallel to the first direction. It is extending. The lower holding part 422 is formed in the shape of a rectangular parallelepiped, and a plurality of lower rollers 423 are arranged close to each other on the upper surface thereof. The lower rollers 423 of the first and second clamping means 4A, 4B are rotatably supported by the lower clamping part 422 about rotational axes parallel to the first direction, and the third and fourth clamping means 4C, The lower roller 423 of 4D is rotatably supported by the lower holding part 422 about a rotation axis parallel to the second direction. The lower roller 423 is attached with about half of its outer peripheral surface protruding from the upper surface of the lower holding part 422.

The upper clamping mechanism 43 disposed above the lower clamping mechanism 42 has a configuration that is generally vertically symmetrical to the lower clamping mechanism 42, and extends toward the inside where it is supported to be vertically movable along the guide rail 412a. It has an arm part 431 and an upper clamping part 432 fixed to the tip of the arm part 431 perpendicularly to the arm part 431 and disposed opposite to the lower clamping part 422, and is configured in a substantially T-shape. ing. A base end portion 431c of the arm portion 431 passes through the guide hole 412c and is disposed within the outer guide groove 412b.

The upper clamping parts 432 of the first and second clamping means 4A, 4B extend parallel to the second direction, and the upper clamping parts 432 of the third and fourth clamping means 4C, 4D extend parallel to the first direction. There is. The upper holding part 432 is formed in the shape of a rectangular parallelepiped, and a plurality of upper rollers (not shown), which will be described later, are arranged close to each other on the lower surface thereof. These upper rollers are arranged to face each other in pairs with the lower rollers 423 of the lower clamping section 422, and the upper rollers of the first and second clamping means 4A, 4B are centered around a rotation axis parallel to the first direction. The upper rollers of the third and fourth clamping means 4C and 4D are rotatably supported by the upper clamping part 432 about rotational axes parallel to the second direction. There is. The upper roller is attached with about half of its outer peripheral surface protruding from the lower surface of the upper holding part 432.

The lower clamping mechanism 42 and upper clamping mechanism 43 are reciprocated in the vertical direction relative to the support portion 412 along the guide rail 412a by a lower moving mechanism 44 and an upper moving mechanism 45, respectively.

The lower moving mechanism 44 is provided with a threaded rod 441 that is screwed into the base end 421c of the arm portion 421 and extends in the vertical direction along the guide groove 412b, and a lower end of the guide groove 412b. It has a pulse motor 442 that rotates in forward and reverse directions. The upper end of the threaded rod 441 is rotatably supported by a bearing 443 fixed within the guide groove 412b. The base end 421c into which the threaded rod 441 is screwed is sent up and down along the guide groove 412b according to the rotational direction of the threaded rod 441 that is rotationally driven by the pulse motor 442, whereby the lower clamping mechanism 42 is moved up and down. be moved.

The upper moving mechanism 45 disposed above the lower moving mechanism 44 has a configuration that is generally vertically symmetrical to the lower moving mechanism 44, and is screwed into the base end 431c of the arm portion 431, and is threaded into the guide groove 412b. It has a threaded rod 451 that extends in the vertical direction along the vertical direction, and a pulse motor 452 that is disposed at the upper end of the support part 412 and drives the threaded rod 451 in forward and reverse rotation. The lower end of the threaded rod 451 is rotatably supported by a bearing 453 fixed within the guide groove 412b. The base end 431c, into which the threaded rod 451 is screwed, is sent up and down along the guide groove 412b according to the rotational direction of the threaded rod 451, which is rotationally driven by the pulse motor 452, thereby causing the upper clamping mechanism 43 to move up and down. I am made to do so.

The control means 7 sends an operation control signal to each pulse motor 52 of the first to fourth moving means 5A to 5D. The control means 7 controls the operation of each pulse motor 52 according to a prescribed program, thereby causing the first and second clamping means 4A, 4B to move in the first direction, and the third and fourth clamping means 4C, 4D to move in the first direction. control the movement of in the second direction.

Next, a structure related to preventing the sheet from slipping will be explained.
FIG. 3 is a diagram showing a state in which the sheet 1 is sandwiched between the upper roller 433 of the upper clamping part 432 and the lower roller 423 of the lower clamping part 422.

The upper roller 433 and the lower roller 423 are rotatable and sandwich the sheet 1 from above and below, and allow the sheet 1 to stretch in the horizontal direction of the page in FIG. By moving the upper clamping part 432 and the lower clamping part 422 in the vertical direction, that is, in the axial direction of each roller, the sheet 1 is stretched in the depth direction of the paper.

The surface of each roller is provided with a non-slip finish 460, as shown in the enlarged portion of the upper roller 433. The anti-slip finish 460 is designed to prevent slipping at the contact points between the sheet 1 and each roller due to tension when the sheet 1 is stretched between the upper and lower rollers. It increases the

In this embodiment, when each roller is made of metal, an anti-slip finish 460 is applied by knurling to form knurling (small protrusions) 462 on the surface of the roller. Thereby, the friction coefficient of the surface of the roller is increased, and the occurrence of slippage of the sheet 1 can be suppressed.

In addition, each roller is made of a resin roller mixed with an inorganic material such as ceramics (e.g., a rubber roller mixed with ceramics, etc.), and the surface of the roller is roughened to ensure a high coefficient of friction. It is also possible to use a stopping process.

Note that the above-described anti-slip processing 460 may be applied to some or all of the rollers, or may be applied only to the upper roller 433 or only to the lower roller 423. In particular, if adhesion of the adhesive layer 12 (FIG. 1) of the sheet to the roller becomes a problem, it is preferable to apply the anti-slip finish 460 only to the lower roller 423.

FIG. 4 shows an example in which an anti-slip process 470 is applied to the contact area of the back surface 1b of the sheet 1 that contacts the lower roller 423 (FIG. 3).
As described above, by applying the anti-slip finish 470 to the sheet 1 side in the contact area between the sheet 1 and the roller, the friction coefficient of the back surface 1b of the sheet 1 is increased, and the occurrence of slipping of the sheet 1 can be suppressed. Can be done.

In the sheet 1 shown in FIG. 4, an adhesive layer 12 is formed on the upper surface 11a of the base material 11, and unevenness 11c is formed on the lower surface 11b of the base material 11. The unevenness 11c realizes an anti-slip process 470 that increases the friction coefficient of the lower surface 11b of the base material 11 (the back surface 1b of the sheet 1). The unevenness 11c may be formed by, for example, blasting (irregularity processing by hitting an abrasive material), but is not particularly limited.

In the example of the sheet 1 shown in FIG. 4, the anti-slip processing 470 on the back surface 1b is applied to areas along the edges of the four sides to be held, thereby forming a square-shaped held part 480. However, an anti-slip finish 470 may be applied to the entire back surface 1b of the sheet 1.

The anti-slip processing of the rollers and the non-slip processing of the sheet described above may be performed simultaneously, or either one of them may be performed.

Next, a description will be given of expansion of a sheet employing the configuration described above.
<Pinch step>
As shown in FIGS. 5A and 5B, a pair of first clamping means 4A and a second clamping means 4B face each other in the first direction, and a pair of third clamping means 4C face each other in the second direction. Both ends of the sheet 1 in the first direction and both ends of the sheet 1 in the second direction are held by the fourth holding means 4D. A workpiece 10 on which a modified layer is formed along a dividing line 101 is attached to the sheet 1 .

<Extension step>
Next, as shown in FIGS. 6(A) and 6(B), the pair of first clamping means 4A and second clamping means 4B are moved in a direction away from each other in the first direction, and the pair of third clamping means 4C and The fourth clamping means 4D is moved in the second direction away from each other.

The sheet 1 is expanded, and the workpiece 10 is broken along the dividing line to be separated into chips 10a.

At this time, the four sides of the sheet 1 are securely clamped by the first clamping means 4A to the fourth clamping means 4D, respectively, and the non-slip processing 460 (FIG. 3) and 470 (FIG. 4) ensure that the four sides of the sheet 1 are securely clamped by the respective rollers. Since the occurrence of slippage is suppressed, it may not be possible to expand the area sufficiently and form a region that is not divided into chips 10a, or the chips may not be able to form a sufficient gap between the chips 10a and come into contact with each other during subsequent handling. This reduces the risk of damaging the chip.

Further, the specific configuration of the expansion device used to carry out the present invention is not limited to the configuration of the expansion device 2 shown in FIG. It can be applied in the form of

The present invention can be realized as described above.
That is, as shown in FIGS. 1 to 6,
A method for expanding a sheet 1 to which a workpiece 10 is attached, the method comprising:
A pair of first direction clamping means (first clamping means 4A, second clamping means 4B) facing each other in the first direction, and a pair of second direction clamping means (first direction clamping means) facing each other in a second direction perpendicular to the first direction. A clamping mechanism including a third clamping means 4C, a fourth clamping means 4D),
A pair of first direction clamping means (first clamping means 4A, second clamping means 4B) each has an upper clamping part 432 and a lower clamping part 422. A plurality of rollers 433 that rotate around a rotation axis parallel to the first direction are arranged, and a plurality of rollers 423 that rotate around a rotation axis parallel to the first direction are arranged on the upper part of the lower holding part 422.
A pair of second direction clamping means (third clamping means 4C, fourth clamping means 4D) each has an upper clamping part 432 and a lower clamping part 422. A plurality of rollers 433 that rotate around a rotation axis parallel to the second direction are arranged, and a plurality of rollers 423 that rotate around a rotation axis parallel to the second direction are arranged on the upper part of the lower holding part 422. a preparation step of preparing the expansion device 2;
a pinching step of pinching a portion of the sheet 1 located on the outside of the workpiece 10 with a plurality of rollers 423 and 432 of the pinching mechanism;
A pair of first direction clamping means (first clamping means 4A, second clamping means 4B) are moved in directions away from each other, and a pair of second direction clamping means (third clamping means 4C, fourth clamping means 4D) are moved. an expansion step for expanding the sheet 1 by moving it in directions away from each other;
A method for expanding a sheet 1, in which at least one of the rollers 423 and 432 of the expansion device 2 and the pinched portion 480 of the sheet 1 that is pinched by the rollers 423 and 432 of the pinching mechanism is subjected to anti-slip processing. It is something to do.

According to the expansion method described above, the occurrence of slippage between the rollers is suppressed, and it is possible to prevent the formation of areas that cannot be expanded sufficiently and are not divided into chips, or the formation of sufficient gaps between chips. It is possible to reduce the risk of the chips coming into contact with each other during subsequent handling and damaging the chips.

1 Sheet 1b Back surface 2 Sheet expansion device 3 Holding table 4A First clamping means 4B Second clamping means 4C Third clamping means 4D Fourth clamping means 10 Workpiece 10a Chip 11 Base material 11a Upper surface 11b Lower surface 11c Unevenness 12 Adhesive layer 42 Lower side Clamping mechanism 43 Upper clamping mechanism 101 Planned dividing line 412c Guide hole 421 Arm part 421c Base end 422 Lower clamping part 423 Lower roller 432 Upper clamping part 433 Upper roller 460 Machining 470 Machining 480 Clamped part

Claims (3)

A method of expanding a sheet to which a work is attached, the method comprising:
A clamping mechanism including a pair of first direction clamping means facing each other in a first direction, and a pair of second direction clamping means facing each other in a second direction orthogonal to the first direction,
The pair of first direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of rotatable shafts that are rotatable around a rotation axis parallel to the first direction. A roller is disposed, and a plurality of rollers rotatable about a rotation axis parallel to the first direction are disposed at the upper part of the lower holding part,
The pair of second direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of screws rotatable around a rotation axis parallel to the second direction. a preparation step of preparing an expansion device in which a plurality of rollers are disposed at the upper part of the lower holding part and are rotatable around a rotation axis parallel to the second direction;
a clamping step of clamping a portion of the sheet located outside the work with the plurality of rollers of the clamping mechanism;
an expansion step of expanding the sheet by moving the pair of first direction clamping means in a direction away from each other and moving the pair of second direction clamping means in a direction away from each other;
The roller of the expansion device is anti-slip treated.
A sheet expansion method characterized by: A method of expanding a sheet to which a work is attached, the method comprising:
A clamping mechanism including a pair of first direction clamping means facing each other in a first direction, and a pair of second direction clamping means facing each other in a second direction orthogonal to the first direction,
The pair of first direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of rotatable shafts that are rotatable around a rotation axis parallel to the first direction. A roller is disposed, and a plurality of rollers rotatable about a rotation axis parallel to the first direction are disposed at the upper part of the lower holding part,
The pair of second direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of screws rotatable around a rotation axis parallel to the second direction. a preparation step of preparing an expansion device in which a plurality of rollers are disposed at the upper part of the lower holding part and are rotatable around a rotation axis parallel to the second direction;
a clamping step of clamping a portion of the sheet located outside the work with the plurality of rollers of the clamping mechanism;
an expansion step of expanding the sheet by moving the pair of first direction clamping means in a direction away from each other and moving the pair of second direction clamping means in a direction away from each other;
A gripped portion of the sheet that is gripped by the rollers of the gripping mechanism is treated with an anti-slip finish;
A sheet expansion method characterized by: A method of expanding a sheet to which a work is attached, the method comprising:
A clamping mechanism including a pair of first direction clamping means facing each other in a first direction, and a pair of second direction clamping means facing each other in a second direction orthogonal to the first direction,
The pair of first direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of rotatable shafts that are rotatable around a rotation axis parallel to the first direction. A roller is disposed, and a plurality of rollers rotatable about a rotation axis parallel to the first direction are disposed at the upper part of the lower holding part,
The pair of second direction clamping means each have an upper clamping part and a lower clamping part, and the lower part of the upper clamping part has a plurality of screws rotatable around a rotation axis parallel to the second direction. a preparation step of preparing an expansion device in which a plurality of rollers are disposed at the upper part of the lower holding part and are rotatable around a rotation axis parallel to the second direction;
a clamping step of clamping a portion of the sheet located outside the work with the plurality of rollers of the clamping mechanism;
an expansion step of expanding the sheet by moving the pair of first direction clamping means in a direction away from each other and moving the pair of second direction clamping means in a direction away from each other;
Anti-slip processing is applied to the roller of the expansion device and the pinched portion of the sheet that is pinched by the roller of the pinching mechanism;
A sheet expansion method characterized by: