JP4746579B2 - Low load conveyor - Google Patents

Description

  The present invention relates to a low-load transport apparatus, and more particularly to a low-load transport apparatus that sucks and transports a substrate with a negative pressure.

In the manufacturing process of an electronic device, for example, when a substrate such as a semiconductor substrate or a glass substrate is transported, a substrate suction transport device that sucks the substrate (wafer) to a predetermined position by sucking the substrate (wafer) to a movable suction head is used. ing.
As this substrate suction transfer device, a suction head having a plurality of suction holes on a support surface, a negative pressure generating means that is connected to the suction head and generates a negative pressure inside each suction hole, and moves the suction head The thing of the structure provided with the moving means to make it known is known (for example, refer patent document 1 and 2).

By the way, when a thin substrate is sucked and transported by the substrate sucking and transporting device, a large stress is applied only to a portion of the substrate in contact with the suction head, and the substrate may be cracked. In particular, in the case where the substrate is a silicon wafer obtained by slicing a silicon ingot, the surface has irregularities and is easily broken at the concave portions.
As a method for suppressing such substrate cracking, (1) the negative pressure is controlled using a vacuum regulator to reduce the stress applied to the substrate by the suction head, and (2) the entire substrate is sucked and unitized. A jig for reducing stress per area is attached to the suction head, or (3) a porous pad (open cell) having elasticity is attached to the suction head, so that the porous pad adheres to the substrate surface. The method of reducing the stress applied to the substrate has been taken.
JP 2004-18256 A JP 2006-27795 A

  However, in the method (1), the substrate stress at the suction head tends to decrease, but the supporting area at several percent or less of the entire substrate area remains the same, and it is not possible to eliminate the cause of the crack. It was enough. In the method (2), the jig is made of a metal such as tungsten, ceramic, or the like, so that the surface is hard, and there is a risk of cracking due to the jig coming into contact with the substrate. Such a substrate is difficult to support because of the large amount of air leakage during adsorption. In the method (3), when tens of thousands of substrates are sucked and conveyed per day, for example, foreign matters such as fine debris peeled off from the substrate surface clog the minute continuous bubbles in the porous pad and suck them. Since the force decreases and it becomes difficult to support the substrate, it is necessary to replace the porous pad with a new one each time.

  The present invention has been made in view of such a problem, and provides a low-load transfer device that can reduce stress applied to a substrate to suppress substrate cracking and reduce maintenance costs.

Thus, according to the present invention, the suction head portion that sucks and supports the substrate by negative pressure, the negative pressure generating means for generating a negative pressure inside the suction head portion, and the substrate sucked by the suction head portion. The suction head unit is attached to the support surface of the head main body unit and has a plurality of air intake holes, and the suction head unit is attached to the support surface of the head main body unit. and is composed of a suction sheet portion having a plurality of through holes communicating said suction seat is made from the pressure-sensitive adhesive sheet head that is peelably to the supporting surface of the body portion, the adhesive sheet, When the surface having adhesiveness that contacts the support surface of the head main body, the surface that does not have adhesiveness that contacts the substrate, and the plurality of through holes, and the adhesiveness decreases. Washing with water Low load transport apparatus is provided comprising a thermoplastic elastomer revived adhesive drying.
According to another aspect of the present invention, an adsorption head unit that adsorbs and supports a substrate with a negative pressure, a negative pressure generating unit that generates a negative pressure inside the adsorption head unit, and the adsorption head unit Transporting means for transporting the sucked substrate, and the suction head portion is attached to the support surface of the head body portion, the head body portion having a plurality of air intake holes on the support surface facing the substrate, and An adhesive sheet having a plurality of through-holes communicating with a plurality of intake holes, the adhesive sheet being releasably attached to a support surface of the head body, and the adhesive sheet The pressure-sensitive adhesive sheet has an adhesive surface that comes into contact with the support surface of the head main body and an adhesive property that comes into contact with the elastic porous sheet. A surface that, said a plurality of through holes, and when the adhesive is lowered, low-load transport apparatus is provided comprising a thermoplastic elastomer restored sticky by washing and drying.

According to the present invention, when the substrate is sucked and supported by the suction head portion, the suction sheet portion scratches the substrate following the uneven surface or the wavy surface of the substrate by the flexibility of the thermoplastic elastomer. It adheres softly without any problems. Therefore, it is possible to reduce substrate stress by reducing the stress on the substrate, and it is possible to adsorb the substrate by suppressing the amount of air leaking in air from the gap between the adsorption sheet portion and the substrate, resulting in insufficient adsorption power Will not occur. Therefore, the low-load transport apparatus of the present invention is suitable for transporting valuable and easily cracked substrates such as solar cell substrates.
Further, the adsorbing sheet portion can be peeled off from the head main body portion and washed with water when a foreign matter adheres to the surface or through hole that contacts the substrate. Therefore, it can be avoided that the foreign matter adhering to the suction sheet portion is pressed against the surface of the substrate and scratches, and that the foreign matter is clogged in the through hole and the suction force of the suction head portion to the substrate is reduced. Moreover, since the adhesive strength is recovered when dried, the suction sheet portion after washing can be reused, and the labor and cost of frequently replacing the suction sheet portion with a new suction sheet portion can be reduced.

The low-load transport device of the present invention sucks the suction head unit that sucks and supports the substrate by negative pressure, negative pressure generating means for generating a negative pressure inside the suction head unit, and the suction head unit. And a suction unit that is mounted on the support surface of the head body and has a plurality of suction holes. It is composed of a suction sheet portion having a plurality of through-holes communicating with holes Ru.
Further, the suction sheet portion is made of the head main body portion affixed that adhesive sheet can be peeled off the support surface of the, or a pressure-sensitive adhesive sheet, the elastic porous to be peelably to the adhesive sheet It consists of a quality sheet.

In the present invention, examples of the substrate include semiconductor substrates and glass substrates used in the manufacture of solar cells and electronic devices, and also include wafers obtained by slicing a semiconductor ingot, and substrates having electrodes, wirings, elements, and the like. To do.
The low-load transfer device of the present invention is as thin as about 100 to 300 μm and can be suitably used for transfer of a substrate having a size of about 170 mm in length × 170 mm in width. For example, a substrate for solar cells sliced from a silicon ingot Is optimal.

In the present invention, if the head main body of the suction head can suck and support the substrate without stress due to negative pressure, its shape, size, number of intake holes, size and arrangement pattern, installation on the conveying means The number and the like are not particularly limited.
For example, in the head body, a plurality of air intake holes are formed in a uniform matrix on one surface (support surface) of an internal hollow metal box or plate body, and the other surface on the side opposite to the one surface or the peripheral side surface is negative. It can be set as the structure which formed the connection pipe part connected with a pressure generation means and exhausting internal air. The surface on which the intake holes are formed becomes a support surface that supports the substrate.

The size of the head main body and the number of installation on the conveying means may be one if the head main body is configured to be as large as the substrate that is the object to be adsorbed, or a predetermined number of locations on the substrate. A plurality of small head main body portions may be installed so as to be attracted.
Moreover, the occupation aperture ratio of the intake holes occupying the entire support surface can be, for example, about 3 to 20%, although it depends on the substrate size and the number of suction head units installed. Further, the arrangement pattern of the air intake holes on the support surface is not particularly limited, and can be appropriately designed according to the substrate size, the transport method, etc. For example, the air intake holes are evenly distributed over the entire surface of the substrate. it can. Also, in the mechanism in which the wafer is conveyed by a conveyor or walking beam, the conveyance part passes through the center, and it is a mechanism that attracts from above the wafer and reverses 180 degrees (reversing the front and back). However, since the suction is performed locally, the suction holes are not evenly aligned on the wafer.

Adhesive sheet of the suction sheet portion is of a thermoplastic elastomer having a support surface substantially the same size and formed in the shape sticky head main body, comparable to a plurality of air intake holes of the head body portion in a size And it can produce by forming the sheet | seat which has multiple through-holes by the same arrangement | positioning.
Here, in the present invention, the thermoplastic elastomer is also called a thermoplastic rubber or an elastoplastic, and is plasticized and fluidized at a high temperature necessary for molding, and exhibits a rubber-like physical property at a normal temperature. It means a polymer having properties.
Examples of the thermoplastic elastomer include polyurethane elastomers, polystyrene elastomers, polyolefin elastomers, and the like. In the present invention, a pressure-sensitive adhesive sheet can be prepared using a commercially available thermoplastic elastomer or a sheet thereof.

In the present invention, the pressure-sensitive adhesive sheet made of a thermoplastic elastomer is obtained by forming a plurality of protrusions in advance on a mold for molding the thermoplastic elastomer into a sheet shape, and heating the mold to add a thermoplastic elastomer to which fluidity is imparted. The pressure-sensitive adhesive sheet having a plurality of through holes formed in the shape and arrangement corresponding to the protrusions of the mold can be produced by pouring the thermoplastic elastomer sheet that has been cooled and solidified from the mold.
Moreover, when forming a several adhesive hole in a commercially available thermoplastic elastomer sheet which does not have a through-hole, and producing an adhesive sheet , it punches using a punch. Alternatively, it is possible to use a Thomson blade that can be accurately and accurately punched in advance.

In the present invention, the adsorbing sheet portion has a first form consisting only of the above-mentioned pressure-sensitive adhesive sheet and a second form in which an elastic porous sheet described later is adhered to the pressure-sensitive adhesive sheet .

In the first embodiment, the adsorbing sheet portion made of the pressure-sensitive adhesive sheet has adhesiveness only on the surface of the sheet that is affixed to the support surface of the head main body portion, and is adhesive on the surface that contacts the substrate. Does not have.
Thus, the adsorption sheet part (adhesive sheet | seat ) which has adhesiveness only on one side can be produced by forming a through-hole by the above-mentioned method in the commercially available thermoplastic elastomer sheet which has adhesiveness only on one side. Moreover, when using the commercially available thermoplastic elastomer sheet which has adhesiveness on both surfaces, the adsorption sheet part can be produced by performing the process which reduces the adhesiveness of one surface, and forming a through-hole. Moreover, when using the adsorption sheet | seat part produced by pouring a thermoplastic elastomer into the above-mentioned type | mold, since it has adhesiveness on both surfaces, the process which reduces the adhesiveness of one side is performed.
The treatment for reducing the tack of the adhesive sheet, for example, clays that are normally added to the thermoplastic elastomer, the non-reinforcing fillers such as talc is attached to one side of the adhesive sheet, or one side of the non-reinforcing Examples thereof include a method in which a pressure-sensitive adhesive sheet is produced so as to increase the concentration of the filler, or a commercially available liquid material that lowers the adhesiveness is applied to one side of the pressure-sensitive adhesive sheet .
The thickness of the pressure-sensitive adhesive sheet in this case is not particularly limited, and can be, for example, about 1 to 5 mm.

In the first form of the adsorbing sheet portion, the pressure-sensitive adhesive sheet can be brought into close contact with the uneven or corrugated shape of the substrate surface due to the excellent flexibility of the thermoplastic elastomer, so that the load on the substrate is kept small. Can be absorbed, and cracking of the substrate can be suppressed. In addition, the adhesive sheet can be releasably attached to the head body due to the adhesiveness of the thermoplastic elastomer, and if it gets dirty, the adhesive sheet can be washed with water and dried to reproduce the adhesive strength Can be reused.

In the second embodiment, by forming a commercially available thermoplastic elastomer sheet in the through hole in the manner described above with sticky sheet both surfaces to form a PSA sheet, laminated elastic porous sheet on one side of the adhesive sheet It is possible to produce an adsorbing sheet part. In this case, the thickness of the pressure-sensitive adhesive sheet can be, for example, about 1 to 5 mm.

  As the elastic porous sheet, a thermoplastic resin sheet having open cells or a non-woven fabric made of thermoplastic resin fibers can be used, but considering use in a clean manufacturing site that does not like dust and dust. In the case of a nonwoven fabric, a thermoplastic resin sheet having open cells is preferable because it may fly due to fiber cutting or fraying. Such a porous thermoplastic resin sheet can be made of foamed plastics such as polyurethane and polyethylene, and commercially available products can be used.

  As this elastic porous sheet, a sheet having a thickness of about 0.1 to 2.0 mm is used depending on the degree of unevenness on the surface of the substrate. For example, when the unevenness of the substrate surface is 20-30 μm, the thickness of the elastic porous sheet is set to about 0.1 mm, and when the unevenness of the substrate surface is 5 μm, the thickness of the elastic porous sheet is about 1-2 mm. Can be set. However, the values are not limited to these values because the thickness of the substrate, the surface state, and the relationship between the substrate thickness and the sheet thickness may be a reverse combination.

Thus, the suction sheet portion of the elastic porous sheet was adhered to the adhesive sheet, adjusting the thickness of the elastic porous sheet according to the degree of unevenness of the substrate surface, i.e. the elastic porous sheet larger irregularities degree By increasing the thickness of the surface to follow the uneven surface, it is possible to control the amount of air leakage and change the adsorption force without a vacuum regulator, and at the time of adsorption than the case of only the adhesive sheet It is possible to improve the stress dispersion effect and the vacuum pressure reduction effect.

In the present invention, the transport means is not particularly limited as long as it can transport the suction head portion that has sucked the substrate to a predetermined position. For example, the suction head portion is attached to a robot arm movable in a three-dimensional direction. It can be set as the structure attached, or the structure which attached the adsorption | suction head part to the frame type trolley | bogie which reciprocates on a guide rail so that raising / lowering is possible.
Moreover, as a negative pressure generation means, it can be set as the structure which connected the vacuum pump and the said connection pipe part of an adsorption | suction head part with the flexible hose.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating a first embodiment of a low-load conveyance device according to the present invention, and FIG. 2 is a bottom view illustrating a support surface of a head main body portion of a suction head portion in the first embodiment.
This low-load transport device is provided with an adsorption head unit 10 that adsorbs and supports the substrate 1 with negative pressure, a negative pressure generating means 20 that generates a negative pressure inside the adsorption head unit 10, and an adsorption head unit 10 And a transport means 30 for transporting the processed substrate 1. FIG. 1 exemplifies the case of a silicon wafer obtained by slicing a silicon ingot to a thickness of about 200 μm as the substrate 1. This silicon wafer has irregularities on the surface, but the degree of irregularities is higher than that of an actual silicon wafer. It is exaggerated. Further, the suction head portion in FIG. 1 shows a cross section when cut along the line AA in FIG.

The suction head portion 10 includes a head main body portion 11 formed from an internal hollow metal plate having substantially the same size as the substrate 1, and a suction sheet portion 12 adhered and adhered to the support surface 11 a of the head main body portion 11. It consists of.
As shown in FIGS. 1 and 2, the head main body 11 has a plurality of air intake holes 11b formed in a uniform matrix shape on the support surface 11a and on the other surface opposite to the support surface 11a. A connecting pipe portion 11c connected to the negative pressure generating means 20 is provided. In this case, the head main body 11 is formed in a square of, for example, 125 to 170 mm, and the suction holes 11b can be formed in a diameter of 1.0 to 5.0 mm and a pitch of 1.0 to 20.0 mm vertically and horizontally. Note that the diameter of the intake holes 11b and the number per unit area may be partially changed.

The suction sheet portion 12 is an adhesive sheet made of a thermoplastic elastomer having adhesiveness only on the surface 12 a that adheres to the support surface of the head main body portion 11, and the size is substantially the same as the size of the head main body portion 11. Yes, the thickness is 1-5 mm. Further, the suction sheet portion 12 is formed such that a plurality of through holes 12b penetrating in the thickness direction thereof are in communication with the diameter and arrangement of the air intake holes 11b of the head main body portion 11 substantially. In addition, this single-sided adhesive adsorbing sheet part 12 forms a through-hole 12b in a thermoplastic elastomer sheet (for example, Pro-7 Proseven manufactured by Pro Seven Co., Ltd. or a gel of human skin manufactured by Exeal Corporation Co., Ltd.). It can produce by doing.

The negative pressure generating means 20 includes a vacuum pump 21 that is driven by a motor, and a flexible hose 22 that connects the vacuum pump 21 and the connecting pipe portion 11 c of the head main body portion 11 of the suction head portion 10. In this case, the vacuum pump 21 may be a pump that can make the inside of the head main body 11 have a negative pressure of 1 MPa or less.
The conveying means 30 is a robot arm that can move in a three-dimensional direction.

When the substrate is sucked by the low-load transport device, the suction head unit 10 is moved to a position near the upper portion of the substrate 1 on the substrate mounting table 2 by the transport unit 30 and the vacuum pump 21 is driven to move the head main body unit. The substrate 1 can be floated and adsorbed to the adsorption head unit 10 (adhesive sheet) by generating a vacuum pressure in the air 11 and sucking outside air from the through holes 12b and the air intake holes 11b. Alternatively, the suction head unit 10 is lowered toward the substrate 1 to bring the suction sheet unit 12 into close contact with the surface of the substrate 1, and then the vacuum pump 21 is driven to generate a vacuum pressure in the head main body unit 11. The substrate 1 can be adsorbed.

  FIG. 3 shows a state in which the substrate 1 is sucked to the suction sheet portion 12 of the suction head portion 10 in the first embodiment. In this state, the suction surface 12c of the suction sheet portion 12 elastically deforms and adheres following the uneven shape or the wavy shape of the surface of the substrate 1, so that the substrate 1 is hardly stressed. Accordingly, the substrate 1 can be transported to a predetermined position without breaking the substrate 1 in a low load state. And the board | substrate 1 is made to detach | leave from the adsorption | suction sheet | seat part 12 by stopping the vacuum pump 21 in a predetermined position. At this time, since the suction surface 12c of the suction sheet portion 12 is not sticky, the substrate 1 is easily separated from the suction sheet portion 12.

In this way, when the substrate 1 is repeatedly transported by the low-load transport device, foreign matters such as silicon powder and fine silicon pieces peeled off from the surface of the silicon wafer as the substrate 1 adhere to the suction surface 12b of the suction sheet portion 12. There is a case. Since the suction sheet portion 12 has excellent flexibility, the suction surface 12c of the suction sheet portion 12 is elastically deformed even if foreign matter is sandwiched between the substrate 1 and the suction sheet portion 12, so that the substrate surface is Although it is difficult to be damaged, a gap causing air leakage is easily formed between the substrate 1 and the suction sheet portion 12 due to the foreign matter. In addition, foreign matter may accumulate in the through holes 12b of the suction sheet portion 12, and the suction force may be reduced.
Therefore, the suction sheet portion 12 can be peeled off from the head main body portion 11 and washed with water to remove foreign matter, and the adhesiveness is restored after drying, so that the suction sheet portion 12 is again attached to the head main body portion 11 by adhesion. Can be used by pasting. Therefore, it is possible to reduce the labor and cost of frequent replacement with a new suction sheet portion.

(Embodiment 2)
FIG. 4 is a schematic configuration diagram showing Embodiment 2 of the low-load conveyance device of the present invention.
The low-load conveyance device of the second embodiment is different from the first embodiment in that the adsorbing sheet portion 114 is adhered to the adhesive sheet 112 made of a thermoplastic elastomer having adhesiveness on both surfaces 112a and 112c, and the adhesive sheet 112. The other structure is the same as that of the first embodiment. In FIG. 1, the negative pressure generating means and the conveying means are not shown, and the same components as those in the first embodiment are denoted by the same reference numerals.
Hereinafter, the configuration of the second embodiment different from that of the first embodiment will be mainly described.

In this case, the pressure-sensitive adhesive sheet 112 has a thickness of 1.0 to 5.0 mm, and is a thermoplastic elastomer sheet (for example, a product name Pro-7 Pro Seven manufactured by Pro Seven Co., Ltd. or a product name human skin gel manufactured by EXCEL Corporation). It can be produced by forming the through hole 112b.
The thickness of the elastic porous sheet 113 is 0.1 to 2.0 mm. For example, a trade name Sunmap LC manufactured by Nitto Denko Corporation can be used.

  According to this low-load conveyance device, a vacuum pump (not shown) is driven to generate a vacuum pressure in the head main body portion 11, so that external air passes through the open cell holes of the elastic porous sheet 113. By sucking air from the through holes 112b and the intake holes 11b, the substrate 1 can be floated and adsorbed to the elastic porous sheet 113 of the adsorption head unit 110. Alternatively, the suction head unit 110 is lowered toward the substrate 1 to bring the elastic porous sheet 113 into close contact with the surface of the substrate 1, and then the vacuum pump is driven to generate a vacuum pressure in the head body 11. The substrate 1 can be adsorbed.

FIG. 5 shows a state in which the substrate 1 is adsorbed to the elastic porous sheet 113 of the adsorption head unit 110 in the second embodiment. In this state, the adsorption surface 113a of the elastic porous sheet 113 mainly elastically deforms and the surface 112c of the adhesive sheet 112 also elastically deforms following the uneven shape of the surface of the substrate 1, so that the substrate 1 is almost stressed. It does not take. Further, since the negative pressure in each through-hole 112 b is distributed almost uniformly over the entire surface of the elastic porous sheet 113, air leakage in which air flows from between the end of the elastic porous sheet 113 and the substrate 1 occurs. No reduction in vacuum pressure can be prevented. In addition, when the unevenness degree of the substrate 1 is large, the elastic porous sheet 113 can reliably follow the uneven surface of the substrate 1 by adjusting the thickness of the elastic porous sheet 113 so that the end portion as described above Air leakage from the air can be controlled without using a vacuum regulator.

In this way, when the substrate 1 is repeatedly transported by the low-load transport device, the above-mentioned foreign matter passes through the elastic porous sheet 113 and adheres to the adhesive sheet 112, and the adhesive force with the elastic porous sheet 113 decreases. In addition, the adsorption resistance may increase due to staying in the micropores in the elastic porous sheet 113. Therefore, the adhesive sheet 112 is peeled off from the head main body 11, and a pressure-sensitive adhesive sheet 112 was peeled off the elastic porous sheet 113 is dried off the foreign matter is washed with water, the adhesive sheet tackiness was restored A new elastic porous sheet can be attached and used.

It is a schematic block diagram which shows Embodiment 1 of the low load conveyance apparatus of this invention. FIG. 3 is a bottom view showing a support surface of a head main body portion of the suction head portion in Embodiment 1. It is sectional drawing which shows the state by which the board | substrate was adsorb | sucked to the adhesive sheet of the adsorption | suction head part in Embodiment 1. 6 is a cross-sectional view illustrating a suction head unit according to Embodiment 2. FIG. It is sectional drawing which shows the state by which the board | substrate was adsorb | sucked to the elastic porous sheet of the adsorption | suction head part in Embodiment 2.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate mounting base 10, 110 Adsorption head part 11 Head main body part 11a Support surface 11b Intake hole 11c Connection pipe part 12 Adsorption sheet part (adhesive sheet )
12a, 112a, 112c Surface 12b, 112b Through-hole 12c, 113a Adsorption surface 20 Vacuum generating means 21 Vacuum pump 22 Flexible hose 30 Conveying means 112 Adhesive sheet 113 Elastic porous sheet 114 Adsorption sheet portion

Claims (5)

An adsorption head unit that adsorbs and supports a substrate by negative pressure, a negative pressure generation unit that generates a negative pressure inside the adsorption head unit, and a conveyance unit that conveys the substrate adsorbed by the adsorption head unit. ,
The suction head unit has a head main body having a plurality of air intake holes on a support surface facing the substrate, and a plurality of through holes attached to the support surface of the head main body and communicating with the plurality of air intake holes. It consists of an adsorption sheet part,
The suction seat is made from the pressure-sensitive adhesive sheet head that is peelably to the supporting surface of the body portion,
The pressure-sensitive adhesive sheet has an adhesive surface that comes into contact with a support surface of the head main body, a non-adhesive surface that comes into contact with the substrate, and the plurality of through holes, and the adhesive sheet. A low-load conveying device comprising a thermoplastic elastomer whose adhesiveness is restored by washing and drying when the property is lowered . An adsorption head unit that adsorbs and supports a substrate by negative pressure, a negative pressure generation unit that generates a negative pressure inside the adsorption head unit, and a conveyance unit that conveys the substrate adsorbed by the adsorption head unit. ,
The suction head unit has a head main body having a plurality of air intake holes on a support surface facing the substrate, and a plurality of through holes attached to the support surface of the head main body and communicating with the plurality of air intake holes. It consists of an adsorption sheet part,
The adsorbing sheet part is composed of an adhesive sheet that is detachably attached to the support surface of the head body part, and an elastic porous sheet that is detachably attached to the adhesive sheet,
The pressure-sensitive adhesive sheet has a surface having adhesiveness that comes into contact with a support surface of the head body portion, a surface having adhesiveness that comes into contact with the elastic porous sheet, and the plurality of through holes, and A low-load transporting device comprising a thermoplastic elastomer whose tackiness is restored by washing and drying when the tackiness is lowered . The low-load conveyance device according to claim 2 , wherein the elastic porous sheet is made of a thermoplastic resin sheet having open cells. The low-load conveyance device according to claim 2 or 3, wherein the elastic porous sheet has a thickness of 0.1 to 2.0 mm.   The low-load transport apparatus according to claim 1, wherein the substrate is a solar cell substrate.

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