JP2012176852A - Vacuum chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum chuck that definitely positions and holds the whole substance along the surface of an attraction pad even if it is a sheet-like attracted body whose periphery is warped relatively to the surface of the attracted body.SOLUTION: The intake area VE is set at the region of the surface in the attraction pad that positions and holds the periphery of the sheet-like attracted body, and the rate of an air flow passing through the intake area VE is increased to increase attraction power to the surface even if the periphery is away from the surface of the attraction pad by enlarging conductance Cn1 per unit area of the intake area than conductance Cn2 per unit area of the surface in the attraction pad excluding the intake area.

Description

  The present invention relates to a vacuum chuck that depressurizes a sealed back side with a vacuum pump and adsorbs and positions an object to be adsorbed placed on the surface of the suction pad through a number of gaps communicating from the surface to the back side. More particularly, the present invention relates to a vacuum chuck that reliably positions a sheet-like object to be adsorbed partially placed away from the surface of the suction pad along the surface of the suction pad due to, for example, remaining curl.

  In a vacuum chuck that sucks and holds the object to be adsorbed through a through-hole communicating with the surface and the back surface, the back side is reduced by a vacuum pump with respect to the surface of the suction pad that sucks the object to be adsorbed. It is necessary to keep the back pressure on the back side close to vacuum with respect to the atmospheric pressure on the side. In such a vacuum chuck, if the object to be adsorbed does not cover the entire surface that is the adsorption surface, a part of the through hole opens to the surface, and outside air flows through the through hole, and the differential pressure between the front side and the back side As a result, there is a problem that a predetermined adsorption force cannot be obtained.

  Thus, a vacuum chuck is known in Patent Document 1 and Patent Document 2 in which a large number of through holes communicating with the front surface side and the back surface side of the suction pad have a small diameter to reduce the conductance of the entire through hole. According to these conventional vacuum chucks, even if some of the through holes are not covered with the object to be adsorbed and opened on the surface, the flow rate flowing from the surface to the back side through the through holes is limited, and the front side and the back side Can be kept constant, and even an object to be adsorbed placed on a part of the surface can be positioned and held on the surface with a predetermined adsorbing force.

Japanese Utility Model Publication No. 43-16175

Japanese Patent No. 2693720

  The vacuum chuck using the above-described conventional suction pad is used for the purpose of temporarily positioning and holding the workpiece on the surface of the suction pad in the machining process of the workpiece, but the workpiece is pulled out from a roll or the like. In the case of the flexible sheet, the curl was left, and when it was placed on the surface of the suction pad, the tip part warped upward, and there was a problem that it could not be positioned flatly along the surface of the vacuum chuck. .

The adsorption force for adsorbing an object to be adsorbed, which is a workpiece, is proportional to the differential pressure ΔP between the atmospheric pressure P1 on the surface side of the suction pad and the atmospheric pressure P2 on the back side sucked by the vacuum pump. The ultimate pressure of the pump is Pu, the exhaust efficiency is Se, and the conductance of the suction pad is C.
ΔP = (P1−Pu) · Se / (Se + C) (6)

  However, the above-mentioned vacuum chuck having a certain exposed area without covering the entire surface of the suction pad has a limit in reducing the pressure P2 on the back side, and the warping of the tip portion is caused by the suction pad. A sufficient adsorbing force for sucking up to the surface of the film could not be obtained.

  Although it has been thought that by reducing the conductance C of the suction pad in the equation (6), an adsorption force until the warped tip is adsorbed is obtained, the adsorption force of the object to be adsorbed obtained from the differential pressure ΔP. Is a value calculated under the condition that the object to be adsorbed covers the opening of the through-hole that appears on the surface of the suction pad, so that the tip of the flexible sheet that warps upward and is separated from the surface of the suction pad is Even if the conductance C is lowered, the surface cannot be adsorbed, which is an obstacle to processing into a flexible sheet.

  Also, when a flat flexible sheet is positioned and held along the outer peripheral surface of the cylinder by a suction roll whose suction pad is a cylindrical body, the tip of the flexible sheet is separated from the surface of the suction pad. Since it is mounted, it may be impossible to adsorb to the outer peripheral surface of the suction roll.

  Therefore, even the object to be adsorbed placed on a part of the surface is placed on the surface of the suction pad, even the above-described conventional vacuum chuck that can be positioned and held on the surface with a predetermined attracting force. In this case, the sheet-like object to be adsorbed in which a part of the surface and the gap is formed is not able to be adsorbed and positioned and held along the surface of the adsorbing pad.

  The present invention has been made in consideration of such conventional problems, and even if it is a sheet-like adsorbent whose peripheral part is curved relative to the surface of the adsorbent, the entire An object of the present invention is to provide a vacuum chuck that reliably positions and holds along the surface of the suction pad.

  In order to achieve the above-mentioned object, the vacuum chuck according to claim 1 is provided with a suction pad made of a porous substrate whose whole side surface is sealed and whose surface and back surface communicate with each other by a large number of gaps. A vacuum chuck that depressurizes the back side of the substrate with a vacuum pump, sucks a sheet-like object to be placed on the surface of the suction pad through a gap, and positions and holds the object along the surface. An intake area is set at the surface area of the suction pad for positioning and holding the peripheral part of the object, and the conductance Cn1 per unit area of the intake area is made larger than the conductance Cn2 per unit area of the surface of the suction pad excluding the intake area It is characterized by that.

  In the intake area below the periphery of the sheet-like adsorbent, the conductance Cn1 per unit area is large, so the flow rate flowing into the gap of the adsorption pad increases, and there is a gap between the periphery of the sheet-like adsorbent and the surface of the adsorption pad. Even if there is, the sheet-shaped adsorbent is pressed against the surface of the intake area by the wind pressure flowing from the front side to the back side of the intake area, and is positioned and held along the surface.

  Since the suction area for positioning and holding the periphery of the sheet-like object to be adsorbed is a part of the entire surface of the suction pad, the conductance Cn1 per unit area of the suction area is expressed as the unit area of the surface of the suction pad excluding the suction area. Even if it is larger than the perimeter conductance Cn2, the pressure P2 on the back surface side is reduced, and in the state where the exposed area (area not covered by the adsorbed substance) is generated on a part of the surface, Sufficient adsorption force for positioning and holding can be obtained.

  In the vacuum chuck according to claim 2, the suction pad is made of a porous substrate having a curved surface, and an intake region is set at a portion of the surface of the suction pad that positions and holds the tip of the sheet-like object to be sucked. The flat sheet-like object to be placed placed on the surface of the suction pad is positioned and held along the surface of the convex curved surface.

  Even if there is a gap between the tip of the flat sheet-like adsorbent and the surface of the suction pad, the tip of the sheet-like adsorbent is pressed against the surface of the intake area by the wind pressure flowing from the front side of the intake area to the back side. And is positioned and held along the surface which is a convex curved surface.

  The vacuum chuck according to claim 3 is characterized in that a large number of gaps are formed in the suction pad with substantially equal density, and a plurality of first concave grooves are provided in the back surface of the suction pad set in the suction area.

  The space of the suction pad is formed with substantially equal density, and the thickness of the portion where the first groove is provided is thinner than the other parts in the surface and the inner top surface of the first groove on the back side. Since the average distance of the air gap communicating between the front surface and the back surface in the intake region is reduced in proportion to the average thickness, the conductance Cn1 per unit area of the intake region is equal to the unit area of other parts excluding the intake region. It becomes larger than the conductance Cn2.

  In the vacuum chuck according to claim 4, a second groove that intersects with the plurality of first grooves and communicates between the intersecting first grooves is formed on the back surface of the suction pad set in the suction area. It is characterized by.

  Since the thickness of the surface of the intake region and the inner top surfaces of the first and second grooves are thinner than those other than the portion other than the intake region, the conductance Cn1 per unit area of the intake region excludes the intake region It becomes larger than the conductance Cn2 per unit area of the other part.

  The vacuum chuck according to claim 5 is characterized in that the suction pad is a porous ceramic substrate.

  Since the suction pad is made of a porous ceramic substrate, voids with a small diameter of 1 μm to 20 μm that communicate with the surface and the bottom surface are formed with high density, and the exposed pad conductances Cn1 and Cn2 are easily reduced to generate an exposed region. Even if it does, the adsorption | suction force which positions and holds a sheet-like to-be-adsorbed object can be generated.

  According to the invention of claim 1, the sheet-like object to be adsorbed in which the curl remains and the peripheral part is warped upward can be reliably positioned and held along the flat surface of the suction pad. The sheet-like object to be adsorbed can be reliably positioned and maintained along the surface of the suction pad that curves into a convex curved surface.

  According to the invention of claim 2, even if the suction pad is composed of a cylindrical body or a part of the porous substrate of the cylindrical body, the flat sheet-like object to be adsorbed is surely adsorbed along the cylindrical surface. Positioning. Therefore, if a suction pad is used for the suction roll, the transported flat flexible film can be reliably positioned and supported along its surface.

  According to the third aspect of the present invention, the conductance Cn1 per unit area of the intake area can be calculated as the conductance per unit area of the surface of the suction pad excluding the intake area by a simple process of forming the first concave groove in the intake area. It can be larger than Cn2.

  Since the entire suction pad is not thinned and only the first groove is formed from the surface, the conductance Cn1 per unit area of the intake region can be increased while maintaining the strength of the suction pad.

  The first groove is recessed from the back surface of the suction pad, and no groove is formed on the surface of the suction area. Therefore, even if the suction force increases at the recessed portion of the first groove, the sheet-shaped object is bent. Or can be positioned and held without leaving a suction mark on the sheet-like object to be adsorbed.

  According to the invention of claim 4, since the plurality of first concave grooves communicate with each other through the second concave grooves, the variation in the suction force in the intake area is reduced, and the sheet-like object is positioned and held without bending. can do.

  According to the fifth aspect of the present invention, since the suction pad is formed of a ceramic substrate, it is sufficient to reduce the thickness or to provide a large number of concave grooves in order to increase the conductance Cn1 per unit area of the intake region. Strength can be obtained.

FIG. 1 is an explanatory view showing a state in which a sheet-like object W is placed on a vacuum chuck 1 according to an embodiment of the present invention. FIG. 2 is a perspective view of the suction pad 2 as viewed obliquely from below. It is a partial abbreviated rear view of the suction pad 2. It is an AA line end view of FIG. FIG. 4 is an end view taken along line BB in FIG. 3. FIG. 6 is an explanatory view showing the suction operation of the vacuum chuck 1. FIG. 7 is an explanatory diagram showing a suction operation in a state where the sheet-like object W is placed on the suction pad 2.

  Hereinafter, a vacuum chuck 1 according to an embodiment of the present invention will be described with reference to FIGS. The vacuum chuck 1 is a part of a printer or a printed circuit board manufacturing apparatus for the purpose of temporarily positioning and holding the flexible sheet W on the surface while performing processing such as printing and wiring on the flexible sheet W. It is incorporated as a mechanism, and is particularly suitable for positioning and holding a flexible sheet W cut to a predetermined length from a strip-like flexible sheet wound around a cylindrical drum 11 as shown in FIG. In other words, even the flexible sheet W in which the curl remains on the cylindrical drum 11 or the feed roller 7 and the leading end Wf in the feed direction is curved and warps upward is attracted and positioned along the surface. .

  The vacuum chuck 1 seals the suction pad 2 that sucks the flexible sheet W from the back side and positions and holds the flexible sheet W on the surface thereof, and seals all the side surfaces of the suction pad 2 and blocks the back side of the suction pad 2 from the outside air. The chuck body 4 serving as the decompression chamber 3, the vacuum pump 5 exhausting from the exhaust passage communicating with the decompression chamber 3, and the flow meter for detecting the exhaust amount per unit time in order to detect the exhaust efficiency Se of the vacuum pump 5 However, the flow meter 6 may be removed after detecting the displacement.

  The suction pad 2 is formed of a porous ceramic substrate, and in the present embodiment, a ceramic substrate is used in which voids having an average pore diameter of 10 μm are formed at an equal density therein, and the porosity n is 35%. An infinite number of voids are continuously formed inside, so that a large number of through-holes communicating with the surface and the back surface per unit area are formed in parallel, and between the surface and the back surface of the suction pad 2. Conductance can be examined.

  Here, the porosity n is the ratio of the volume of the voids per unit volume of the suction pad 2, but the voids communicating from the front side to the back side are formed in the suction pad 2 with equal density. For example, the ratio of the total opening area of the voids opened in the unit area to the unit area (for example, 1 square centimeter) of the surface of the suction pad 2 is proportional to the porosity n with a constant determined from the shape and size of the voids. Here, the opening ratio to the surface of the void is represented by the porosity n. If the ceramic sintering technique is used, a porous ceramic substrate can be formed with an average pore diameter in the range of 1 to 200 μm and a porosity n in the range of 10 to 60%. If the porosity n is less than 20%, In some cases, a part of the through-hole is blocked, and the calculated adsorption force may not be obtained. If it is 60% or more, the voids increase, the strength deteriorates, and there is a risk of breakage.

  As shown in FIG. 2, the area of the surface of the suction pad 2 below the peripheral portion (here, the front end portion Wf in the feeding direction) placed on the flexible sheet W in an upward direction is an intake region VE. The conductance Cn1 per unit area of the intake area VE is set to a larger value than the conductance Cn2 per unit area of the other suction pads 2.

  As means for increasing the conductance Cn1 per unit area of the intake area VE as compared with other areas, the thickness of the suction pad 2 of the intake area VE is reduced, the porosity n of the intake area VE is increased, and the average pore diameter of the voids In the present embodiment, a plurality of horizontal concave grooves 8 and a plurality of vertical concave grooves perpendicular to the horizontal concave grooves 8 are formed on the back surface of the suction pad 2 where the intake area VE is set. 9 is recessed to increase the conductance Cn1 per average unit area of the intake region VE.

That is, in the portion where the horizontal groove 8 and the vertical groove 9 shown in FIGS. 3 to 5 are recessed, the distance between the surface and the inner top surface of the groove is the surface of the suction pad 2 other than the intake region VE. shorter than the distance L ₂ between the rear, conductance is inversely proportional to the distance of the gap which communicates the back surface. Therefore, the conductance per unit area of the portion where the concave grooves 8 and 9 are recessed increases, and the average conductance Cn1 per unit area in the entire intake region VE also increases.

A thickness of L ₂ porous L ₁ the average thickness of the intake region VE due to the recessed concave grooves 8, 9 on a ceramic _substrate, a thickness per unit area of the suction pad 2 except the intake region VE of L ₂ The conductance Cn1 per average unit area of the intake region VE is Cn1 = (L ₂ / L ₁ ) · Cn2, where L ₁ / L ₂ is k ₁ (0 <k ₁ <1), where conductance is Cn2. If
Cn1 = Cn2 / k ₁ ... (1)

In the equation (1), k ₁ is a real number where 0 <k ₁ <1. Therefore, the equation (1) represents the conductance Cn1 per average unit area of the intake region VE by providing the concave grooves 8 and 9. Indicates that the average conductance Cn2 per unit area in the region other than the intake region VE increases. In this specification, the average conductance Cn1 per unit area in the entire intake area VE is calculated as the conductance Cn1 per unit area and the entire area other than the intake area VE, unless otherwise required for explanation. The average conductance Cn2 per unit area will be described as conductance Cn2 per unit area.

Since voids are formed at equal density in the suction pad 2, the number of voids connecting the front surface and the rear surface per unit area in parallel is constant, and the conductance C1 of the entire intake region VE is the surface area of the intake region VE. as _{S 1,} and C1 = Cn1 · _{S 1,} conductance C2 of the suction pad 2 except the intake region VE is the surface area of the non-suction region VE as _{S 2,} respectively represented by C2 = Cn2 · _{S 2.} Therefore, the conductance C ′ of the suction pad 2 as a whole by forming the concave grooves 8 and 9 is C ′ = Cn1 · S ₁ + Cn2 · S ₂ , and S ₁ / S _{2 is set} to k ₂ (0 <k ₂ < 1) Substituting equation (1),
C ′ = Cn2 · S ₂ · (k ₁ + k ₂ ) / k ₁ ·· (2).

On the other hand, the conductance C of the suction pad 2 when the recessed grooves 8 and 9 are not recessed in the intake region VE is C = Cn2 · (S ₁ + S ₂ ) and S ₁ = S ₂ · k ₂ . Using equation (2)
C ′ / C = (k ₁ + k ₂ ) / (k ₁ + k ₁ · k ₂ ) ·· (3)

In the equation (3), k ₁ is a real number of 0 <k ₁ <1, and therefore, if the denominator and the numerator of the equation (3) are compared, k ₁ + k ₂ > k ₁ + k ₁ · k ₂ , The expression (3) indicates that the conductance C ′ of the suction pad 2 having the recessed grooves 8 and 9 recessed is larger than the conductance C of the suction pad 2 having no recessed grooves 8 and 9.

  As shown in FIG. 6, using the suction pad 2 made of a porous ceramic substrate, the pressure in the decompression chamber 3 (hereinafter referred to as the back) when evacuated from the decompression chamber 3 of the vacuum chuck 1 by the vacuum pump 5 having the ultimate pressure Pu. P2) (assuming pressure) is assumed to be a cylinder whose diameter is sufficiently smaller than the mean free path λ of gas molecules,

It is represented by In the equation (4), P1 is the atmospheric pressure on the surface side of the suction pad 2, Se is the exhaust efficiency of the vacuum pump 5 measured by the flow meter 6, r is the radius of the cylinder, L is the length of the cylinder, k is the Boltzmann constant, T is the absolute temperature, m is the mass of the gas molecule, q is the number of voids communicating with the entire front and back of the suction pad 2, and q1 is the number of voids of the suction pad 2 covered with the flexible sheet W. It is.

  (4) in the formula

Represents the conductance C of the suction pad 2 when the recessed grooves 8 and 9 are not recessed, and as shown in FIG. 6, q1 is 0 when the flexible sheet W is not placed. ,
Equation (4) is
P2 = (Pu + P1 · C / Se) / (1 + C / Se) (5)

Using the equation (5), the differential pressure ΔP between the atmospheric pressure P1 and the back pressure P2 is
ΔP = P1−P2 = (P1−Pu) · Se / (Se + C) (6)

Further, as shown in FIG. 6, a vacuum pump of the ultimate pressure Pu from the decompression chamber 3 to be blocked by using the suction pad 2 in which the concave grooves 8 and 9 are provided in the intake region VE and the overall conductance is C ′. The back pressure P2 ′ when exhausting with the same exhaust efficiency Se in FIG.
P2 ′ = (Pu + P1 · C ′ / Se) / (1 + C ′ / Se) (5) ′ where the differential pressure ΔP ′ between the atmospheric pressure P1 and the back pressure P2 ′ is
ΔP ′ = P1−P2 ′ = (P1−Pu) · Se / (Se + C ′) (7)

From Equation (6) and Equation (7),
ΔP ′ / ΔP = (Se + C) / (Se + C ′) (8), and by substituting equation (3) into equation (8) and deleting C ′,
ΔP ′ / ΔP = (Se + C) / [Se + C · (k ₁ + k ₂ ) / (k ₁ + k ₁ · k ₂ )] (9) where the coefficient of the denominator C coefficient (k ₁ + k ₂ ) / Since (k ₁ + k ₁ · k ₂ ) is a real number of 1 or more, it is shown that the differential pressure ΔP ′ is reduced by providing the concave grooves 8 and 9.

The airflow rate Qn ′ sucked from the front surface to the back surface per unit area of the intake region VE is represented by Qn ′ = ΔP ′ · Cn1 from the definition of conductance, and is similarly a region where the concave grooves 8 and 9 are not provided. The air flow rate Qn sucked from the front surface to the back surface per unit area is expressed as Qn = ΔP · Cn2.
Qn ′ / Qn = ΔP ′ · Cn1 / ΔP · Cn2 (10). If the equations (1) and (9) are substituted into the equation (10) and rearranged, the equation (10) becomes
Qn ′ / Qn = (Se + C) / [k ₁ · Se + C · (k ₁ + k ₂ ) / (1 + k ₂ )] (11) Here, if the Se coefficients of the denominator and numerator are compared, 1> k ₁ , and if the coefficients of C of the denominator and numerator are compared, 1> (k ₁ + k ₂ ) / (1 + k ₂ ), Both have small denominator coefficients. Therefore, although the differential pressure ΔP ′ is reduced by forming the concave grooves 8 and 9, the air flow rate Qn ′ increases conversely, and the leading end of the flexible sheet W warped upward in the intake region VE by the wind pressure. The portion Wf can be sucked and positioned and held reliably along the surface.

  That is, in order to adsorb the object to be adsorbed away from the surface of the adsorption pad 2, the conductance per unit area of the adsorption pad at the distant part is increased and the pressure difference ΔP between the atmospheric pressure P1 and the back pressure P2 is increased. Increasing the adsorption force by increasing the adsorption force has been considered as a countermeasure. However, as a result of intensive studies by the inventors of the present application, the increase in the adsorption force by increasing the differential pressure ΔP is caused by the adsorbed object W on the surface. In order to adsorb the object to be adsorbed W away from the surface, the conductance of the part is rather decreased, and the air flow rate Qn is reduced even if the overall differential pressure ΔP is decreased. We found that it is necessary to increase

  However, according to the present embodiment, since the differential pressure ΔP ′ from the back pressure P2 ′ is reduced, the suction force after the flexible sheet W is brought into close contact with the surface of the suction pad 2 is also reduced. Hereinafter, the conditions required for the suction pad 2 to obtain the suction force F equal to or greater than the minimum suction force Fmin, where Fmin is the minimum suction force per unit area for positioning and holding the flexible sheet W along the surface. explain.

  As shown in FIG. 7, when the entire flexible sheet W is placed on the surface of the suction pad 2 whose back pressure is P2 ′, in the opening of the gap covered by the flexible sheet W, The flexible sheet W receives the pressure difference ΔP ′ between the atmospheric pressure P1 and the back pressure P2 ′ in the vertical direction, and the flexible sheet W has a difference pressure ΔP ′ in the sum S2 of the opening areas of all the gaps covered by the flexible sheet W. The adsorption force F multiplied by is received.

If the projected area of the flexible sheet W onto the surface of the suction pad 2 is S1, the total S2 from the porosity n is S1 · n, and the suction force F of the flexible sheet W is
F = nS1 · ΔP ′ (12) expressed by the equation, and the adsorption force Fn per unit area of the flexible sheet W is
Fn = F / S1 = n · ΔP ′ (13)

Furthermore, if the equation (7) is substituted into ΔP ′ in the equation (13), the adsorption force Fn per unit area of the flexible sheet W is
Fn = n · (P1−Pu) · Se / (Se + C ′) (14) In the equation (14), P1 is known as the atmospheric pressure, Pu is known as the ultimate pressure of the vacuum pump 5, and Se is a flow meter during the unit time without the flexible sheet W shown in FIG. Since the flow rate measured at 6 can be measured as the exhaust efficiency of the vacuum pump 5, the adsorption force Fn per unit area by the adsorption pad 2 having the porosity n and the conductance C ′ is obtained from the equation (14).

  Here, the conductance C ′ of the suction pad 2 as a whole is a value in a state where the flexible sheet W is not placed on the surface. When the opening is covered, it increases and the adsorption force Fn per unit area further increases.

Therefore, regardless of the presence or absence of the flexible sheet W, the adsorption force Fn per unit area along the surface is the adsorption force Fn calculated from the equation (14) in a state where the flexible sheet W is not placed. If the minimum adsorbing force Fmin per unit area necessary for adsorbing and holding the flexible sheet W of the vacuum chuck 1 is not decreased,
Fmin ≦ n · (P1−Pu) · Se / (Se + C ′) (15) If the suction pad 2 having a porosity n and a conductance C ′ satisfying the equation (15) is selected, the size of the flexible sheet W can be obtained. Regardless, the vacuum chuck 1 that can reliably position and hold the flexible sheet W can be obtained. Here, the minimum suction force Fmin per unit area varies depending on the thickness and specific gravity of the flexible sheet W. For example, the suction is performed without shifting the position on the suction pad 2 during the work on the flexible sheet W. The minimum adsorption force Fmin for holding is 33 kPa, which is 3/10 of the atmospheric pressure P1.

If the minimum suction force required for positioning and holding the flexible sheet W whose projected area onto the surface of the suction pad 2 is S1 is F ′,
F '= Fmin.S1.ltoreq.n.S1. (P1-Pu) .Se / (Se + C')... By selecting a suction pad 2 having a porosity n and conductance C 'satisfying the equation (16) The flexible sheet W can be reliably positioned and held.

(Example)
An area having a width of 95 mm and a width of 15 mm on which the tip of the flexible sheet W of a porous ceramic substrate having a porosity n of 35%, a size of 100 mm square and a thickness of 5 mm is placed is set as an intake area VE. Then, from the back side of the intake area VE, as shown in FIG. 2 to FIG. 5, six horizontal concave grooves 8 and nine vertical concave grooves 9 are formed so as to intersect to form the suction pad 2. (Hereinafter referred to as suction pad A). As shown in FIG. 4, the horizontal grooves 8 are 1 mm wide and 3 mm deep and recessed from the back side to the surface, and the horizontal grooves 8 are equally spaced with a pitch of 2 mm. The vertical grooves 9 are also 1 mm wide and 3 mm deep and recessed from the back side to the surface. Each vertical groove 9 is orthogonal to each horizontal groove 8 at an equal pitch of 12 mm. 8 communicates with each other.

  Thus, by providing a large number of the horizontal grooves 8 and the vertical grooves 9 in the intake region VE, the distance (thickness) between the inner top surface and the surface at the position where the grooves 8 and 9 are formed. Is 2 mm, and the average thickness of the entire intake region VE is reduced. Therefore, the conductance Cn1 per unit area of the intake region VE is larger than the conductance Cn2 per unit area other than the intake region VE having a thickness of 5 mm. Become.

  As a comparative example of the suction pad A which is an embodiment, the suction pad 2 (hereinafter referred to as the suction pad B) made of a porous ceramic substrate having the same material as the suction pad A, a size of 100 mm square and a thickness of 2 mm, and the suction pad An adsorption pad 2 (hereinafter, adsorption pad C) made of a porous ceramic substrate having the same material as A and a size of 100 mm square and a thickness of 5 mm was prepared. Therefore, the conductance Cn3 per unit area of the suction pad B is larger than the conductance Cn2, the conductance per unit area of the suction pad C is Cn1, and the conductance C of the entire suction pad 2 is the suction pad C, the suction pad A, The suction pad B increases in order.

  Each of the above three types of suction pads A, suction pads B, and suction pads C is placed on the chuck body 4 and all sides are sealed with the chuck body 4, and a vacuum with an ultimate pressure Pu of −96 kPa from the decompression chamber 3 is obtained. The pump 5 exhausted exhaust efficiency Se at 200 L / min.

  First, each back pressure P2 is measured in a state where the object W is not placed on the surface of the suction pad 2, the suction pad A is -69 kPa, the suction pad B is -55 kPa, and the suction pad C is -75 kPa. The result of the above equation (6) in which the differential pressure ΔP between the atmospheric pressure P1 and the back pressure P2 decreases as the conductance C of the entire suction pad 2 increases.

  Next, a flexible sheet W made of a PVC plate having a width of 15 mm, a length of 120 mm, and a thickness of 1 mm is used as the sheet-shaped object to be adsorbed W. For the suction pad A, the flexible sheet W is defined as an intake region VE. Arranged above the intake region VE so as to overlap in the vertical direction, one side in the longitudinal direction was pulled up from the intake region VE, and the adsorption force F in that state was measured. Further, for the suction pad B and the suction pad C, the same flexible sheet W is disposed above the surface area corresponding to the intake area VE, and one side in the longitudinal direction is pulled up from the surface, with the same posture. The adsorption force F of was measured. That is, the state in which the flexible sheet W whose peripheral portion warps upward is placed on each of the suction pads A, B, and C is reproduced in a pseudo manner, and the periphery of the flexible sheet W that warps upward in that state. The force acting in the direction to adsorb the part to the surface of the suction pad 2 was measured as the adsorption force F.

  As a result, the suction force F by the suction pad A is 208 gf, the suction force F by the suction pad B is 204 gf, the suction force F by the suction pad C is 115 gf, and the suction pad having a larger conductance Cn1 per unit area of the suction region VE. When a suction pad B having a larger conductance Cn3 per unit area in a region corresponding to A and the intake region VE is used as the suction pad 2, a large suction force F that attracts the warped peripheral portion to the surface side works. Became clear.

  Subsequently, the back pressure P2 measured in a state where the flexible sheet W whose one side is pulled up from the surface is in close contact with the surface of the suction pad 2 is -75 kPa for the suction pad A and-for the suction pad B. The pressure was 57 kPa and the suction pad C was -74 kPa.

  From these measurement results, the suction pad A and the suction pad B are effective for sucking the peripheral portion of the flexible sheet W away from the surface, but the suction pad B also increases the overall conductance C. After the back pressure P2 is not sufficiently reduced and the entire flexible sheet W is arranged along the surface, the adsorbing force for positioning and holding becomes insufficient, and the whole is thinned. Deteriorate.

  According to the suction pad A according to the embodiment of the present invention, even when a part of the flexible sheet W is placed in a state along the upper side from the surface of the suction pad A, a sufficient suction force to suck the surface is sufficient. In addition, after the entire flexible sheet W is adsorbed along the surface, even if the surface of the remaining adsorbing pad A is not covered with the flexible sheet W, it is flexible at the adsorbing position. Adsorption force sufficient to position and hold the sheet W can be obtained. In addition, since the conductance Cn1 per unit area of a part of the region where the intake region VE is set is merely increased, a predetermined strength can be obtained without reducing the overall thickness.

  In the above-described embodiment, the vacuum chuck that adsorbs and holds the flexible sheet W whose peripheral portion curves upward on the surface of the flat suction pad 2 has been described. However, the porous substrate constituting the suction pad is described above. Is a cylindrical body or a part of a cylindrical body, and a flat flexible sheet W is conveyed onto a suction pad whose surface is curved into a convex curved surface, and the flat flexible sheet W is stomached along the surface of the suction pad. It can also be applied to vacuum chucks that are fixed and held. In this vacuum chuck, an intake region is set at the surface portion of the suction pad corresponding to the tip of the flat flexible sheet W, and the conductance Cn1 per unit area of the intake region is determined per unit area of other surface regions. Larger than the conductance Cn2.

  Further, in the above-described embodiment, the porous ceramic substrate is used as the suction pad 2. However, as long as the porous substrate is used, substrates of various materials and structures can be used as the suction pad 2.

  The area of the suction pad 2 that sets the intake area VE is a part where the peripheral part warped above the sheet-like object to be adsorbed is expected, and is not limited to the surface area of the suction pad 2 shown in the figure. Other positions may be used, and the intake region VE may be set at two or more different positions.

  Further, the means for increasing the conductance Cn1 per unit area in the intake area VE is not limited to the above-described means in which the concave groove is provided, but the overall thickness of the intake area VE is reduced or the density of the air gap is reduced. In addition, a porous substrate having a large inner diameter of each air gap or a porous substrate having a high porosity n is integrally joined to a portion corresponding to the intake region VE with respect to the porous substrate excluding the intake region VE. There may be.

    The present invention provides a vacuum chuck or a flat flexible sheet for positioning and holding a sheet-like adsorbate with a curl remaining on the periphery in a manufacturing process of a semiconductor, a liquid crystal, a printed wiring board, or the like or a printing machine. It is suitable for a suction roll that is positioned and held along its surface.

DESCRIPTION OF SYMBOLS 1 Vacuum chuck 2 Adsorption pad 3 Decompression chamber 5 Vacuum pump 6 Flowmeter W Sheet-like adsorbent (flexible sheet)
Se Exhaust efficiency Pu Ultimate pressure P1 Atmospheric pressure P2 Back pressure VE Intake region

Claims (5)

The suction pad is composed of a porous substrate with the entire side sealed and the surface and back communicate with each other by a number of gaps. The back side of the sealed suction pad is depressurized with a vacuum pump and placed on the surface of the suction pad. A vacuum chuck for sucking a sheet-shaped object to be adsorbed through a gap and positioning and holding the object along the surface,
An intake area is set at the surface area of the suction pad that positions and holds the periphery of the sheet-like object to be adsorbed, and the conductance Cn1 per unit area of the intake area is determined as the conductance per unit area of the surface of the suction pad excluding the intake area. A vacuum chuck characterized by being larger than Cn2. The suction pad is made of a porous substrate whose surface is curved with a convex curved surface, and an intake region is set at the surface of the suction pad that positions and holds the tip of the sheet-like object to be adsorbed, and is placed on the surface of the suction pad. The vacuum chuck according to claim 1, wherein the flat sheet-shaped object to be adsorbed is positioned and held along the surface of the convex curved surface. 3. The suction pad according to claim 1, wherein a number of voids are formed in substantially equal density, and a number of first concave grooves are formed in the back surface of the suction pad set in the intake area. The vacuum chuck according to claim 1. The back surface of the suction pad set in the intake area is provided with a second groove that intersects with the plurality of first grooves and communicates between the intersecting first grooves. The vacuum chuck as described. The vacuum chuck according to any one of claims 1 to 4, wherein the suction pad is a porous ceramic substrate.

Images