JP4124052B2 - Screen printing apparatus and screen printing method - Google Patents

Description

The present invention relates to a screen printing apparatus and a screen printing method for holding a substrate such as a semiconductor wafer in screen printing .

Screen printing is widely used as a method for supplying a solder bonding material such as cream solder to a substrate such as a silicon wafer. In this method, cream solder is printed on the upper surface of the substrate through the pattern holes by sliding the squeegee on the mask plate with the substrate in contact with the lower surface of the mask plate provided with the pattern holes. In this screen printing operation, squeezing for moving the squeegee is followed by plate separation for separating the substrate from the lower surface of the mask plate (see Patent Document 1).
JP-A-7-214748

  Incidentally, in recent years, the range of substrates that are subject to screen printing has been expanded, and screen printing has also been used for supplying solder for forming solder bumps on semiconductor elements in a wafer state. Since such a semiconductor wafer is fragile and difficult to handle and is circular, the semiconductor wafer alone cannot be used as a printing target of the screen printing apparatus, and is handled in a state of being held by a dedicated carrier.

  In addition, with respect to such a semiconductor wafer, the pitch of bumps formed with the finer electronic components is also reduced, and a large number of bumps are formed densely. As the fine pitch is increased, the degree of printing difficulty increases, and it is very difficult to ensure uniform and good release properties, especially over the entire surface of the substrate. However, if the conventional plate separation method is applied to screen printing for fine-pitch substrates held by a carrier, good printing results cannot be obtained, and variations in printing amount, soldering, etc. Various problems occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a screen printing apparatus and a screen printing method that can ensure good plate release properties.

The screen printing apparatus according to claim 1, wherein the substrate is brought into contact with the lower surface of the mask plate in which the pattern hole is formed, and the squeegee is slid on the upper surface of the mask plate to print the paste on the substrate through the pattern hole. in the screen printing apparatus, and the lower member of a substrate support surface for supporting contact with the underside of the base plate is provided, and suction holes for attracting and holding the lower surface of the substrate provided on the substrate supporting surface, said An upper member that is provided on the upper surface of the lower member that supports the substrate and is provided with an opening that fits the substrate, and a mask plate that is formed on the upper surface of the upper member and is flush with the upper surface of the substrate at the printing position. of having a contact with a mask abutment surface on the lower surface, the substrate holding jig for holding the printing position of the mask plate lower surface a substrate by receiving lower, said base holding the substrate A lower receiving portion for mounting a holding jig, and mechanisms to abut the mask abutment surface is raised the lower support on the lower surface of the mask plate, the clamping surfaces formed on the side surface of the upper member was provided with a clamping mechanism for clamping from the side, the mechanism for separating the upper surface of the substrate held by only the lower member of the substrate holding jig is lowered to the bearing portion from the lower surface of the mask plate.

The screen printing method according to claim 2, wherein a lower member provided with a substrate support surface that contacts and supports the lower surface of the substrate, an adsorption hole provided on the substrate support surface for adsorbing and holding the lower surface of the substrate, An upper member that is provided on the upper surface of the lower member that supports the substrate and is provided with an opening that fits the substrate; and is formed on the upper surface of the upper member and is flush with the upper surface of the substrate at the printing position. A substrate holding jig comprising: a mask contact surface that contacts a lower surface of a mask plate; and a clamped surface that is formed on a side surface of the upper member and is clamped from the side by a clamp mechanism of a screen printing apparatus at the printing position. The held substrate is brought into contact with the lower surface of the mask plate in which the pattern hole is formed, and the squeegee is slid on the upper surface of the mask plate to pass through the pattern hole to the substrate. A screen printing method for printing a strike, wherein the substrate holding jig holding the substrate to be printed is carried to the printing position and placed on a receiving portion; and vacuum suction from the suction hole Then, a suction step for sucking and holding the substrate, a clamping step for clamping only the upper member by the clamp mechanism, and a mask for bringing the lower surface of the mask plate into contact with the substrate and the mask contact surface relatively A mounting step; a squeegeeing step of printing a paste on the substrate through the pattern hole by sliding a squeegee on the upper surface of the mask plate; and the lower receiving portion while maintaining the clamp state of the upper member by the clamping mechanism A plate separating step of separating the upper surface of the substrate held only by the lower member from the lower surface of the mask plate by lowering The jig receiving step for raising the lower receiving portion again to unite the lower member and the upper member to restore the substrate holding jig, and carrying out the substrate holding jig holding the printed substrate Process.

  According to the present invention, the substrate holding jig for holding the substrate is composed of the upper and lower layers of the upper member and the lower member, and only the upper member is clamped by the clamping mechanism during printing, and the upper member is kept in the clamped state when separating the plate. With the lower receiving portion lowered, the upper surface of the substrate held only by the lower member is separated from the lower surface of the mask plate, so that the plate can be separated while suppressing downward deflection of the mask plate. It is possible to ensure good release properties over the entire surface.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 and 4 are side views of a screen printing apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of the screen printing apparatus according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. 5 is a perspective view of a substrate holding jig for screen printing, FIG. 5 is a flowchart of a screen printing method according to an embodiment of the present invention, and FIGS. 6 and 7 illustrate steps of the screen printing method according to an embodiment of the present invention. FIGS. 8A and 8B are explanatory diagrams of the plate separation operation in the screen printing method according to the embodiment of the present invention.

  First, the structure of the screen printing apparatus will be described with reference to FIGS. In FIG. 1, the screen printing apparatus is configured by arranging a substrate positioning unit 1 below a screen printing unit 11. The substrate positioning unit 1 is configured by stacking a Y-axis table 2, an X-axis table 3, and a Z-axis table 4, and placing a receiving unit 6 thereon. The Z-axis table is provided with a first Z-axis mechanism for moving the lifter plate 4b up and down with respect to the horizontal base plate 4a and a second Z-axis mechanism for moving up and down the receiving portion 6 with respect to the lifter plate 4b. It has become.

  The first Z-axis mechanism has a configuration in which a feed screw 4c that is rotationally driven by a lifting motor is vertically arranged on a base plate 4a, and a nut member that is screwed to the feed screw 4c is fixed to the lifter plate 4b. . The second Z-axis mechanism has a structure in which a feed screw 4d that is rotationally driven by a lifting motor is vertically arranged on a lifter plate 4b, and a nut member that is screwed to the feed screw 4d is fixed to the lower receiving portion 6. It has become. In addition, illustration of a raising / lowering motor and a nut member is abbreviate | omitted also with the 1st, 2nd Z-axis mechanism.

The receiving unit 6 receives a substrate holding jig 7 (hereinafter abbreviated as “carrier 7”) that holds a semiconductor wafer 9 (hereinafter simply abbreviated as “wafer 9”) as a substrate to be printed. To do. The carrier 7 has a function of receiving the wafer 9 and holding it at a printing position on the lower surface side of the screen printing unit 11. A pair of clampers 5 driven by a clamp mechanism (not shown) is disposed on the lifter plate 4b, and the clampers 5 sandwich and fix the carrier 7 received by the lower receiving portion 6 from both left and right sides. .

  Here, the wafer 9 and the substrate holding jig 7 will be described with reference to FIG. A plurality of semiconductor elements 9a are formed in a lattice shape on the wafer 9, and an external connection electrode provided on the circuit formation surface of the semiconductor elements 9a is a printing target to which cream solder is supplied by screen printing. The carrier 7 includes a lower member 8 of a substantially square plate member and an upper member 10 placed on the lower member 8.

  A convex portion 8 a corresponding to the shape of the wafer 9 is provided on the upper surface of the lower member 8, and the upper surface of the convex portion 8 a is a substrate support surface 8 b that contacts and supports the lower surface of the wafer 9. The substrate support surface 8b is provided with a plurality of suction holes 8c. In a state where the lower member 8 is placed on the lower receiving portion 6, the suction hole 8 c is connected to a vacuum suction means (not shown) via a suction hole (not shown) provided in the lower receiving portion 6. The wafer 9 is sucked and held on the substrate holding surface 8b by vacuum suction from the suction hole 8c.

  The upper member 10 is provided with an opening 10 a having a shape into which the wafer 9 is fitted. The upper member 10 is placed on the upper surface of the lower member 8 in a state where the wafer 9 is supported. As a result, the horizontal position of the wafer 9 is held while the wafer 9 is held by the carrier 7. A positioning convex portion 8d is provided at a diagonal position on the upper surface of the lower member 8, and a concave portion 10b is provided on the lower surface of the upper member 10 at a position corresponding to the convex portion 8d. With the upper member 10 placed on the lower member 8, the upper member 10 is correctly positioned with respect to the lower member 8 by fitting the convex portion 8d into the concave portion 10b. The convex portion 8 d and the concave portion 10 b serve as positioning means for positioning the upper member 10 and the lower member 8.

  As shown in FIG. 4, in a state where the upper member 10 is stacked on the lower member 8 and the wafer 9 is placed on the substrate placement surface 8 b, the upper surface 10 c of the upper member 10 is flush with the wafer 9. Then, the carrier 7 in this state is carried into a printing position below the mask plate 12, and the upper surface 10c of the upper member 10 is moved to the mask plate by driving the Z-axis table 4 to raise the lifter plate 4b and the lower receiving portion 6. 12 is in contact with the lower surface. The upper surface 10c of the upper member 10 is a mask contact surface that is in contact with the lower surface of the mask plate 12 in a state flush with the wafer upper surface at the printing position.

  Here, the width dimension of the upper member 10 is set to be larger than the width dimension of the lower member 8. When the carrier 7 is held at the printing position and clamped by the clamper 5, only the side surface 10 d of the upper member 10 is clamped. 5, the lower member 8 is not clamped. The side surface 10d of the upper member 10 is a clamped surface that is clamped from the side by the clamping mechanism of the screen printing apparatus at the printing position. As shown in FIG. 2, the wafer 9 is carried by the carry-in conveyor 17 while being held by the carrier 7, delivered to the printing conveyor 18, and placed on the receiving unit 6. Then, the printed carrier 7 is carried out by a carry-out conveyor 19.

  In FIG. 1, a screen printing unit 11 is disposed above the substrate positioning unit 1. The screen printing unit 11 includes a mask plate 12 extended on a holder frame. A squeegee unit 13 is disposed on the mask plate 12, and the squeegee unit 13 is moved in the Y direction by a moving means (not shown). The plate 14 of the squeegee unit 13 is provided with a squeegee lifting mechanism 15 that moves the squeegee 16 up and down.

  As shown in FIG. 4, with the wafer 9 held on the carrier 7 in contact with the lower surface of the mask plate 12, the cream solder as paste is supplied onto the mask plate 12 and the squeegee 16 is slid. As a result, cream solder is printed on the connection electrodes provided on the semiconductor elements 9a of the wafer 9 through pattern holes (not shown).

  The screen printing apparatus is configured as described above, and the screen printing method will be described below with reference to FIGS. 6 and 7 along the flow of FIG. First, as shown in FIG. 6A, the carrier 7 holding the wafer 9 to be printed is carried by the printing conveyor 18 to the printing position below the screen printing unit 11 (ST1) and mounted on the lower receiving unit 6. (Loading process).

  Next, as shown in FIG. 6B, the lower receiving portion 6 is raised by the second Z-axis mechanism (ST2), and the lower receiving portion 6 is brought into contact with the lower surface of the lower member 8 to receive the carrier 7. To do. In this state, the upper surfaces of the wafer 9 and the upper member 10 are flush with the upper surface of the clamper 5. Then, vacuum suction is performed from the suction hole 8c (FIG. 3) to suck and hold the wafer 9 on the substrate holding surface 8b of the lower member 8 (ST3) (suction process).

  Thereafter, as shown in FIG. 6C, the clamper 5 is moved by the clamp mechanism, and only the upper member 10 of the carrier 7 is clamped (ST4) (clamping step). Next, as shown in FIG. 6 (d), the substrate positioning unit 1 is driven to align the printing position of the wafer 9 with respect to the mask plate 12 (ST5), and the lifter plate 4b is raised by the first Z-axis mechanism ( ST6) The mask plate 12 is mounted on the wafer 9 with the lower surface of the mask plate 12 relatively brought into contact with the mask contact surfaces of the wafer 9 and the upper member 10 (mask mounting process).

  Then, by driving the squeegee unit 13 and sliding the squeegee 16 on the upper surface of the mask plate 12, the cream solder is printed on the wafer 9 through the pattern holes (ST7) (squeezing step). When the squeezing is completed, as shown in FIG. 7A, the lower receiving portion 6 is lowered by the first Z-axis mechanism while keeping the upper member 10 clamped by the clamper 5 (ST8). . Thereby, the upper surface of the wafer 9 held only by the lower member 8 is separated from the lower surface of the mask plate 12 (plate separating step).

  Next, the lifter base 4b is lowered by the first Z-axis mechanism (ST9), the clamper 5 is separated from the mask plate 12, and the receiving portion 6 is raised again by the first Z-axis mechanism (ST10). The lower member 8 and the upper member 10 are combined vertically to restore the separated carrier 7 (jig restoration process). Then, as shown in FIG. 7C, the clamper 5 is moved to release the clamped state of the upper member 10 (ST11), and then the vacuum suction of the wafer 9 by the lower member 8 is released (ST12). As shown in (d), the carrier 7 holding the wafer 9 by lowering the receiving portion 6 is placed on the printing conveyor 18. Then, by transferring the carrier 7 to the carry-out conveyor 19 (FIG. 2), the carrier 7 holding the printed wafer 9 is carried out (ST14) (unloading step).

  Next, the plate separation process in the above-described screen printing method will be described with reference to FIG. In this printing plate making process, as shown in FIG. 8A, the mask plate 12 is supported from the lower surface side by the upper member 10 fixed by the clamper 5. The separation from the lower surface of the wafer is performed within the range of the plate separation width B1 substantially equal to the outer dimension of the wafer 9. For this reason, when the wafer 9 is lowered, the mask plate 12 adhered to the surface of the wafer 9 is unlikely to bend downward as the wafer is lowered. Sequentially performed stably.

  FIG. 8B shows, for comparison, a plate separation operation in a screen printing method performed by the screen printing apparatus of the present embodiment and using a conventional wafer carrier 7A. In this case, the separation of the wafer 9 from the lower surface of the mask plate 12 is performed within the range of the plate separation width B2 (greater than B1) equal to the distance of the clamper 5, and the edge of the clamper 5 from the outer periphery of the wafer 9 In the range up to the portion, the mask plate 12 is in a state where the lower surface side is free during the plate separation operation.

  For this reason, when the wafer 9 is lowered, the mask plate 12 is lowered while being in close contact with the surface of the wafer 9, and the mask plate 12 is likely to bend downward in a range where the above-described lower surface is free. The separation between the wafer 9 and the mask plate 12 is abruptly generated when the wafer 9 descends to a certain height and the mask plate bending reaction force exceeds the above-mentioned adhesion force, and is printed by this unstable plate separation. This causes printing defects such as solder deformation and uneven printing. This tendency is particularly noticeable when the pattern hole density of the mask plate is high, such as when fine pitch bumps are formed on the wafer.

  On the other hand, when the carrier 7 shown in the present embodiment is used, the lower surface of the mask plate 12 outside the range of the wafer 9 is supported by the upper member 10 that surrounds the outer periphery of the wafer 9 from all directions. Regardless of the directionality, that is, in the X direction where the clamper 5 for clamping the carrier 7 does not exist, the downward deflection of the mask plate 12 at the time of separating the plate can be restricted. Accordingly, it is possible to prevent an unstable detachment operation due to the mask plate which is bent repels at a time due to the bending reaction force. Thus, even when a wafer 9 on which fine pitch bumps are formed, such as a wafer 9 that has a high degree of printing difficulty, uniform and good plate separation can be ensured over the entire surface of the wafer 9.

INDUSTRIAL APPLICABILITY The screen printing apparatus and the screen printing method of the present invention have the advantage of ensuring good plate separation over the entire surface of the substrate, and are useful in the field of screen printing for a substrate such as a semiconductor wafer. .

The side view of the screen printing apparatus of one embodiment of this invention The top view of the screen printing apparatus of one embodiment of this invention The perspective view of the board | substrate holding jig for screens of one embodiment of this invention The side view of the screen printing apparatus of one embodiment of this invention Flow diagram of a screen printing method according to an embodiment of the present invention Process explanatory drawing of the screen printing method of one embodiment of this invention Process explanatory drawing of the screen printing method of one embodiment of this invention Explanatory drawing of plate separation operation | movement in the screen printing method of one embodiment of this invention

Explanation of symbols

1 Substrate positioning part 4 Z-axis table 5 Clamper 6 Base receiving part 7 Carrier (Substrate holding jig)
8 Lower member 9 Wafer 10 Upper member 11 Screen printing unit 12 Mask plate 13 Squeegee unit

Claims (2)

The substrate on a lower surface of the mask plate pattern holes are formed by contact, by sliding the squeegee by the mask plate upper surface in a screen printing apparatus for printing paste on a substrate through the pattern holes, of the base plate A lower member provided with a substrate support surface that contacts and supports the lower surface, an adsorption hole provided on the substrate support surface for adsorbing and holding the lower surface of the substrate, and an opening that fits the substrate are provided. An upper member placed on the upper surface of the lower member that supports the substrate, and a mask contact surface that is formed on the upper surface of the upper member and contacts the lower surface of the mask plate in the same position as the upper surface of the substrate at the printing position. A substrate holding jig for receiving the substrate and holding it at a printing position on the lower surface side of the mask plate; a lower receiving portion for placing the substrate holding jig holding the substrate; A mechanism for abutting the mask abutment surface on the lower surface of the mask plate parts is increased and a clamping mechanism for clamping the clamped surface formed on a side surface of the upper member from the side, the bearing portion A screen printing apparatus comprising a mechanism for lowering and separating the upper surface of the substrate held only by the lower member of the substrate holding jig from the lower surface of the mask plate . A lower member provided with a substrate support surface that abuts and supports the lower surface of the substrate, an adsorption hole provided on the substrate support surface for adsorbing and holding the lower surface of the substrate, and an opening that fits the substrate And an upper member placed on the upper surface of the lower member supporting the substrate, and a mask contact formed on the upper surface of the upper member and contacting the lower surface of the mask plate in the same position as the upper surface of the substrate at the printing position. A pattern hole is formed on a substrate held by a substrate holding jig having a surface and a clamped surface formed on a side surface of the upper member and clamped from the side by a clamping mechanism of a screen printing apparatus at the printing position. A screen printing method in which a paste is printed on the substrate through the pattern holes by contacting the lower surface of the mask plate and sliding the squeegee on the upper surface of the mask plate. Then, a carrying-in process of carrying the substrate holding jig holding the substrate to be printed up to the printing position and placing it on the receiving part, and a suction to hold the substrate by vacuum suction from the suction hole A clamping step of clamping only the upper member by the clamping mechanism, a mask mounting step of bringing the lower surface of the mask plate into contact with the substrate and the mask contact surface, and an upper surface of the mask plate The squeegee slides the squeegee to print the paste on the substrate through the pattern hole, and the lower receiving portion is lowered while the upper member is being clamped by the clamp mechanism. A plate separating step of separating the upper surface of the substrate held only by the member from the lower surface of the mask plate, and the lower member is raised again by the lower member. Screen printing method characterized by comprising the unloading step for unloading the jig recovery process to recover the substrate holding jig up and down combined with said upper member, the substrate holding jig holding the substrate after printing.

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