JP2007196496A - Equipment and method for screen printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide screen printing equipment which is capable of fixing an angle of detachment of a mask from a plate in a printing process, in regard to the screen printing equipment wherein a flux or the like is printed in a prescribed pattern on one side of an electronic component. <P>SOLUTION: The screen printing equipment has an elastic mask which is provided with an opening part corresponding to a printing pattern and with a printing area supplied with a printing material, a supply means which is so disposed as to be movable at least in one direction above the mask, while pressing the mask aligned with a printing object, a raising means which is disposed in the rear of the supply means in the direction of movement of the supply means and moves synchronously with this means, and a mask receiving means which has a mask receiving surface positioned in the rear of the supply means in the direction of movement of this means, between the top of the mask and one side of the raising means facing the mask in the direction vertical to the direction of movement of the supply means, and moves synchronously with this means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a screen printing apparatus and a screen printing method for printing a printing material on a substrate, and in particular, a solder paste, a flux, etc. are printed in a predetermined pattern on a circuit board on which a semiconductor device wafer or electronic component is mounted. The present invention relates to a screen printing apparatus and a screen printing method suitable for the above.

  Hereinafter, the background of the present invention will be described based on a technique of printing a printing material such as solder paste or flux on an electronic component, but the present invention is not limited to the following description.

  For example, when mounting electronic components such as LSIs, capacitor elements, and resistor elements on a circuit board, first, solder paste is printed on the circuit board, then the electronic components are mounted on the solder paste, and solder paste is applied by reflow. Molten and bonded to the circuit board. When solder bumps are formed on a wafer or the like using solder balls, first, the flux is printed on the wafer, then the solder balls are mounted on the flux, and the solder balls are melted by reflow to solder bumps. Is forming.

  The screen printing apparatus used in the process of printing the above solder paste, flux, etc. (hereinafter also referred to as paste including solder paste, flux) on a circuit board or the like has an opening corresponding to the print pattern. A metal screen or a thin metal plate (hereinafter referred to as a mask) is aligned on the circuit board, and then the paste supplied on the upper surface of the mask is spread with a squeegee to fill the opening, and then the mask is removed from the circuit board. It is configured to release the paste and transfer the paste to the circuit board, and two methods, an off-contact method and a contact method, are known.

  Here, the former has a predetermined initial gap G (hereinafter sometimes referred to as snap-off) between the lower surface of the mask 911 and the upper surface of the circuit board W, as shown in FIG. In this method, the paste f is spread while moving while being pressed so as to close the initial gap G with the squeegee 92 and printed on the circuit board W through the opening 913. In this method, the mask 911 immediately after the squeegee 92 passes is released from the circuit board W by the tension of the mask 911 that is pressed by the squeegee 92 and extended by the amount corresponding to the amount of deflection. Here, in this method, as the squeegee 92 moves, the angle (release angle) Θ when the mask 911 is released from the circuit board W changes, so the release state of the mask 911 becomes unstable and printed. There has been a problem in printing quality such as variations in printing accuracy such as the pitch and dimensions of the paste f.

  In the latter, as shown in FIG. 7 (b), the mask 911 is brought into contact with the circuit board W for alignment, so that the print quality and accuracy described above are advantageous. It has come to be used as a system that can cope with the narrowing of wiring pitch accompanying the increase in mounting density. However, in this method, after the printing process is completed, the circuit board W is lowered and the mask 911 is released, so that a separate release process is required, and in order to obtain stable printing quality, the circuit board W is used. There is a problem in that it is necessary to descend at a low speed of 1 mm / second or less, and it takes a long time for the printing work. Also in this method, since the plate separation is performed by the tension of the mask 911, the circuit board W and the mask are different depending on the formation state of the opening 913 of the mask 911 (roughness of the inner wall of the opening, etc.) and the adhesive force of the paste f. When the adhesive strength with 911 is different in each part, the release angle Θ of the mask 911 is not constant, and there is a problem in print quality as in the case of off-contact printing.

  Various studies have been made to solve the above problems, and an example thereof is described in Patent Document 1 below. In Patent Document 1, a mask set so as to be in contact with the surface of a circuit board is moved by soldering by moving the tip from one end side to the other end side of the X axis parallel to the upper surface of the mask and parallel to the upper surface of the mask. A squeegee that pushes the paste into the opening of the mask is provided above the mask, lifting means for lifting one end side of the mask upward and sequentially peeling it from the circuit board, and one end side of the mask with respect to the circuit board centering on the tip of the squeegee Elevating means for elevating and lowering the lifting means so that the inclination angle (release angle) of the squeegee is substantially constant, and the tip of the squeegee and the lifting means are each parallel to the upper surface of the mask and perpendicular to the X axis. A contact-type screen printing apparatus extending in the axial direction is disclosed.

According to this screen printing apparatus, the squeegee moves from one end side to the other end side of the X-axis to push the solder into the opening of the mask, and the lifting device lifts the lifting means so that the one end side of the mask is lifted. Are lifted upward and peeled off sequentially from the circuit board. The lifting means forcibly peels the mask obliquely upward from the other end side with respect to the surface of the circuit board starting from the tip of the squeegee that is in contact with the mask. There is an advantage that the release state is stabilized.
JP 2000-85012 A

  However, the screen printing apparatus of Patent Document 1 has the following problems to be solved. Since the lifting means of Patent Document 1 is configured to mechanically lift the mask, when the mask is positioned on the circuit board, only the position where the circuit board does not exist, specifically, the position corresponding to the end of the mask is arranged. It is possible. Therefore, there is a problem that the lifting means cannot be arranged when there is no room for placing the lifting means due to the size of the mask and the circuit board. Moreover, the lifting means of Patent Document 1 is configured to lift the end of the mask. Therefore, when the edge of the mask is lifted by the lifting means while spreading the paste supplied to the mask with the squeegee, the edge of the mask is centered in the longitudinal direction of the squeegee (direction intersecting or orthogonal to the moving direction of the squeegee). Get away quickly from the club. This is because the mask used in screen printing is usually very thin and has flexibility (elasticity) of several tens to several hundreds of micrometers. For this reason, although the release angle of the mask finally becomes the same angle, it takes more time to reach the angle as it goes to the center of the squeegee, and the release of the mask in the longitudinal direction of the squeegee The state will vary. The variation in the release state has an adverse effect on the print quality as described above. This problem has become more prominent in masks corresponding to recent finer pitch wiring patterns and larger circuit boards and wafers.

  The present invention has been made in view of the above-described problems of the prior art, and a screen printing apparatus and a screen for printing a printing material such as a solder paste or a flux in a predetermined pattern on one surface of a printed material such as an electronic component. In a printing method, a first object is to provide a novel screen printing apparatus and a screen printing method capable of releasing a mask at a predetermined release angle in the process of printing a printing material. Furthermore, a second object of the present invention is to provide a screen printing apparatus and a screen printing method that can make the release state of the mask uniform.

  One aspect of the present invention is a screen printing apparatus that prints a printing material in a predetermined pattern on one surface of a printing medium, an opening corresponding to the pattern, and a printing area that includes the opening and is supplied with the printing material. And a supply means for supplying a printing material to the printing region, arranged to be movable in at least one direction above the mask while pressing the mask aligned with the substrate. And a pulling means that is disposed behind the supply means with respect to the moving direction of the supply means, pulls up the mask while moving in synchronization with the supply means, and is perpendicular to the moving direction of the supply means A mask receiving surface located between the upper surface of the mask in the direction and one surface of the pulling means facing the mask and located behind the supplying means in the moving direction of the supplying means. For example, a screen printing apparatus characterized by having a mask catch means for moving in synchronization with the supply means. The “printing material” is mainly a liquid material, and includes a viscous printing material such as a paste or gel.

  According to the screen printing apparatus described above, the mask is aligned with one surface of the printing medium so as to have a predetermined positional relationship. The supply means moves the upper side of the mask aligned with the substrate to be printed and supplied with the printing material while pressing the mask to spread the printing material on the printing area, thereby printing the opening included in the printing area. Press and fill the material. The pulling-up means disposed behind the supply means and moving in synchronization with the supply means pulls up the mask behind the supply means after the printing material is filled in the opening, so that the mask is removed from the substrate. Release. At this time, the mask receiving surface of the mask receiving means is positioned between the upper surface of the mask and one surface of the pulling means facing the mask in a direction perpendicular to the moving direction of the supplying means, and Since the mask receiving means moves in synchronization with the supply means in the movement direction, the mask pulled up by the pulling means is always in a fixed position in the positional relationship with the supply means. It is received by the mask receiving surface. That is, in the process of printing the printing material, the positional relationship between the contact portion of the supply means that is in contact with the mask and the mask receiving surface is always constant. The peeling angle is always kept constant.

  In addition, if the mask receiving surface is positioned almost at the same position as the lifting means, specifically, directly below the lifting means, it is possible to reliably prevent damage to the mask while keeping the mask release angle constant. And it is suitable at the point which can simplify an apparatus structure. This aspect can be configured by, for example, joining a mask receiving means to one end of the lifting means, or providing a function of the mask receiving means by providing a mask receiving surface on the lifting means itself.

  Further, at least the mask receiving surface is preferably made of a soft material such as plastic, rubber or other resin so that the mask is not damaged. In addition, when it is set as the structure which provides the function of a mask receiving means to the raising means itself as mentioned above, you may form the raising means itself with a soft material. Furthermore, in order to avoid damage to the mask, the mask receiving surface is preferably formed of a curved surface.

  As the pulling-up means, it is possible to adopt a pulling-up means such as a vacuum suction method that sucks and pulls up the mask using a vacuum, or an electrostatic method that sucks and pulls up the mask by static electricity. It is desirable that it is a lifting means (magnetic force generating means) using a magnetic force method for raising. In this case, the mask is made of a soft magnetic material. For example, if the permanent magnet is used as the magnetic force generating means and the mask is pulled up by the magnetic force, the apparatus configuration becomes simple. In addition, a permanent magnet capable of generating a uniform magnetic force as a whole is relatively easy to obtain, and the mask can be uniformly released. As the soft magnetic material constituting the mask, for example, a metal material such as magnetic stainless steel or nickel, or a resin material containing soft magnetic powder can be used. In order to make the release state of the mask uniform, it is preferable that the size of the lifting means is equal to or larger than the size of the printing area.

  In another aspect of the present invention, in a screen printing method for printing a printing material in a predetermined pattern on one surface of a printing material, an elastic mask having an opening corresponding to the pattern is aligned with the printing material, While pressing the mask, it moves from one end of the mask to the other end to supply the printing material to the opening, pulls up the mask after the printing material is supplied to the opening, and has a certain relationship with the pressing position of the mask This is a screen printing method for receiving a mask pulled up at a position.

  As described above, according to the present invention, the printing material supplied to the mask aligned with one surface of the substrate to be printed is pressed into the opening portion by the supply means, filled, and moved relative to the supply means. The mask after the printing material is filled in the opening by the pulling means always at a fixed position in the step is pulled up, and the mask receiving means is always at a fixed position in relation to the supply means. Since it is configured to receive the mask pulled up by the surface, it is possible to always release the mask at a constant release angle in the process of printing the printing material, and as a result, the release state of the mask is stable and extremely printed. A high-quality screen printing apparatus and screen printing method can be provided. Further, by making the size of the lifting means equal to or larger than the size of the printing area, the release state of the mask can be made uniform, and a screen printing apparatus and a screen printing method with high print quality can be provided.

  The present invention will be described based on specific embodiments with reference to FIGS. 1 is a perspective view showing a schematic configuration of a screen printing apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of a wafer as an object of the screen printing apparatus of FIG. 1, and FIG. 3 is an enlarged cross section of the screen printing apparatus of FIG. FIGS. 4 and 5 are sectional views showing a modification of the screen printing apparatus of FIG. 1, and FIG. 6 is a diagram for explaining the operation of the screen printing apparatus of FIG.

  As shown in FIG. 2, the target printing material in the screen printing apparatus of this aspect is a wafer W on which solder balls B having a diameter of about 80 to 150 μm are mounted on flat electrodes p arranged in a predetermined pattern. Yes, a paste-like flux as a printing material is printed on the flat electrode p by screen printing.

  In the screen printing apparatus 1 according to the first aspect, reference numeral 11 denotes a printing unit. The printing unit 11 includes a flat plate-shaped mask 111 stretched from the periphery by an elastic member or a member having elasticity, and a frame-shaped support portion 112 that supports the mask 111. In the mask 111, a plurality of openings 113 corresponding to the arrangement pattern of the flat electrodes p of the wafer W are formed. The mask 111 has a plurality of openings 113 filled with the flux f and a print area 114 that is an area where the flux f is spread, and an upper surface (one surface) of the wafer W on which the plate-like electrodes p are arranged. And a back surface (one surface) 115 aligned with a predetermined positional relationship. The mask 111 is made of magnetic stainless steel and has a thickness of about 50 μm. Note that the thickness of the mask 111 is appropriately set in consideration of the size of the solder balls, the size of the flat electrode p, and the like. The opening 113 can be formed by a known processing method such as laser processing, etching processing, or precision electroforming. Here, the screen printing apparatus 1 employs an off-contact method. Therefore, as shown in FIG. 3A, the mask 111 of the first mode is aligned with the upper surface of the wafer W so that the back surface 115 has a predetermined gap, that is, a snap-off G.

  Reference numeral 15 in FIG. 1 denotes a flat table on which the wafer W is placed. It is preferable to incorporate a vacuum suction means for vacuum-sucking the wafer W into the table 15 because the mounted wafer W is sucked and fixed to the table 15.

  Reference numeral 12 denotes a flat squeegee made of a plastic or rubber material which is the supply means of this embodiment. The squeegee 12 is configured such that the lower end of the squeegee 12 abuts the upper surface of the mask 111 aligned with the wafer W and presses the mask 111 downward. As shown by arrows in FIG. 3, the squeegee 12 is attached to a horizontal moving means 14 that can move horizontally from one end of the mask 111 to the other end. Here, as shown in FIG. 1, the movement direction of the squeegee 12 is the X axis, the direction perpendicular to the X axis in the horizontal plane is the Y axis, and the direction (vertical direction) perpendicular to both the X axis and the Y axis is the Z axis. It is defined as

  As shown in FIG. 3B, the squeegee 12 has a size that can include the print area 114 in the Y-axis direction, and is disposed at a position that can cover the print area 114. Therefore, the squeegee 12 spreads the flux f supplied to the upper surface of the mask 111 on the printing region 114 by the movement in the X-axis direction, and presses and fills the opening 113 with the flux f.

  Reference numeral 13 denotes a permanent magnet (magnetic force generating means) which is a pulling means for pulling up the mask 111 upward as indicated by an arrow in FIG. The permanent magnet 13 is fixed to the horizontal moving means 14 so as to be positioned behind the squeegee 12 in the X-axis direction and above the mask 111 in the Z-axis direction, and maintains a predetermined distance from the squeegee 12. 12 and move in synchronization. Note that the permanent magnet 13 of the present embodiment has a squeegee in the Y-axis direction as shown in FIG. 3B in order to make the release state of the mask 111 along the Y-axis direction, that is, the longitudinal direction of the squeegee 12 uniform. 12 is substantially the same size as 12 and is configured to include the print area 114 of the mask 111. Further, the permanent magnet 13 is configured to include a part of the printing region 114 in the X-axis direction.

  Reference numeral 16 denotes a mask receiving means. Reference numeral 161 denotes a mask receiving surface formed at the lower end of the mask receiving means 16, and a permanent magnet facing the upper surface of the mask 111 and the mask 111 in the Z-axis direction, that is, the direction perpendicular to the moving direction of the squeegee 12. 13 is located at substantially the same position as the squeegee 12 in the moving direction of the squeegee 12. Here, the mask receiving means 16 of this aspect is being fixed to the lower end part of the permanent magnet 13 so that it may unite with the permanent magnet 13, as shown to Fig.3 (a). Therefore, the mask receiving means 16 can move in synchronization with the squeegee 12, and the mask receiving surface 161 is positioned directly below the permanent magnet 13. For example, the permanent magnet 13 may be a molded magnet formed from a soft resin in which magnetic powder is dispersed, and the lower end surface of the permanent magnet 13 may be a mask receiving surface 161. According to such a configuration, the permanent magnet 13 can be given the function of the mask receiving means 16, and the apparatus configuration can be simplified.

  The mask receiving means 16 is made of a resin-based soft material such as plastic or rubber, and the mask receiving surface 161 is formed to have a rounded shape by dropping corners at least in the X-axis direction. The mask 111 that comes into contact with the mask receiving surface 161 is designed not to be damaged. Note that the mask receiving surface 161 is not limited to the substantially trapezoidal shape shown in FIG. 3A. For example, as shown in FIGS. 5A to 5C, the mask receiving surface 161 has a substantially triangular shape (161a) and a concave shape ( 161b) or semicircular (161c).

  The operation of the screen printing apparatus 1 having the above configuration will be described with reference to FIG. First, as shown in FIG. 6A, the wafer W is placed at a predetermined position on a table (not shown), and a predetermined snap-off G is formed between the upper surface of the wafer W and the back surface 115 of the mask 111. Then, the mask 111 is aligned.

  Next, as shown in FIG. 6B, the flux f is supplied to the upper surface of the mask 111, the lower end of the squeegee 12 is brought into contact with the right end (one end) of the mask 111, and the mask 111 is pressed against the wafer W. Since the mask 111 has elasticity, the portion with which the squeegee 12 is in contact is curved downward and contacts the upper surface of the wafer W. Here, the permanent magnet 13 provided at the rear of the squeegee 12 pulls up the mask 111 located below, and the mask receiving surface 161 of the mask receiving means 16 receives the lifted mask 111. As a result, a release angle Θ is formed between the mask 111 and the wafer W with the contact portion of the squeegee 12 in contact with the mask 111 as a starting point.

  Next, as shown in FIG. 6C, the squeegee 12 is moved by the horizontal moving means 14 from the right end of the mask 111 toward the left end (the other end). Along with the movement, the squeegee 12 spreads the flux f on the printing region 114 and fills the opening 113 while pressing the flux f. Since the permanent magnet 13 moves behind the squeegee 12 in synchronism with the squeegee 12, the mask 111 immediately after the opening 113 is filled with the flux f is pulled upward. Here, since the permanent magnet 13 is sized to include the printing area 114, the mask 111 below the permanent magnet 13 is uniformly pulled upward. Since the mask receiving means 16 is moved in synchronization with the squeegee 12 together with the permanent magnet 13, the mask receiving surface 161 receives the pulled up mask 111. Here, the mask receiving surface 161 is configured to maintain a certain positional relationship with the squeegee 12 in the X-axis direction and the Z-axis direction even when the squeegee 12 is moving. The angle Θ can be kept constant. Further, since the mask receiving surface 161 is formed of a soft member, the mask 111 is not damaged. The mask 111 received by the mask receiving means 16 is restored to the initial state having the snap-off G by the restoring force of the mask 111 itself after passing through the mask receiving means 16.

  Next, as shown in FIG. 6D, the squeegee 12 is moved to the left end of the mask 111, and the printing of the flux f is completed.

  The mask receiving means 16 is preferably larger than the size of the printing area 114 so that the mask 111 can be received uniformly from the viewpoint of uniforming the release angle of the mask 111 along the Y-axis direction. . However, for example, when the mask 111 is relatively thick, it may be provided at positions corresponding to both end portions of the mask 111 or may be arranged in parallel along the Y-axis direction. Further, in order to make the release state of the mask 111 uniform, the length of the permanent magnet 13 is set to be equal to or larger than the size of the printing region 114. For example, the mask 111 is relatively small and the uniformity of the release state is increased. When it is not necessary to consider, there is no limitation on the size or arrangement, and it is possible to select appropriately within a range in which the release angle can be made constant in cooperation with the mask receiving means 16.

  The present invention is not limited to the above-described embodiment, and can also be implemented in the embodiment shown in FIG. The screen printing apparatus 2 in FIG. 4 has basically the same configuration as the screen printing apparatus 1 except that the mask receiving means 26 is behind the squeegee 12 and before the permanent magnet 13 in the X-axis direction. Is different. The mask receiving means 26 is fixed to the horizontal moving means 14 so as to have the above positional relationship. The screen printing apparatus 2 having such a configuration can basically release the mask 111 at a constant release angle Θ as in the screen printing apparatus 1, but the mask receiving means 26 is a permanent magnet in the X-axis direction. Therefore, the pulled up mask 111 may come into contact with the permanent magnet 13 and be damaged. However, for example, when the mask 111 is relatively thick and rigid, the screen printing apparatus 2 of this embodiment can sufficiently cope with the problem.

1 is a perspective view illustrating a schematic configuration of a screen printing apparatus according to an aspect of the present invention. It is a perspective view of the wafer which is the object of the screen printing apparatus of FIG. It is the fragmentary sectional view and top view of the screen printing apparatus of FIG. It is a fragmentary sectional view which shows the deformation | transformation aspect of the screen printing apparatus of FIG. It is a partial expanded sectional view which shows the deformation | transformation aspect of the screen printing apparatus of FIG. FIG. 6 is a partial sectional view for explaining the operation of the screen printing apparatus of FIG. It is sectional drawing which shows the conventional screen printing apparatus.

Explanation of symbols

1 (2, 9): Screen printing device 11 (91): Printing means 111 (911): Mask 112 (912): Support portion 113 (913): Opening 114: Printing region 115: Back surface 12: Squeegee 13: Permanent Magnet 14: Horizontal moving means 15: Table 16 (26): Mask receiving means G: Snap off W: Wafer p: Flat electrode f: Flux

Claims (6)

In a screen printing apparatus that prints a printing material in a predetermined pattern on one surface of a substrate,
(1) A mask having elasticity including an opening corresponding to the pattern and a printing region including the opening and supplied with a printing material;
(2) Supply means for supplying the printing material to the printing area, which is arranged so as to be movable in at least one direction above the mask while pressing the mask aligned with the substrate.
(3) a pulling unit disposed behind the supply unit with respect to the moving direction of the supply unit, and pulling up the mask while moving in synchronization with the supply unit;
(4) It is located between the upper surface of the mask and one surface of the pulling means facing the mask in a direction perpendicular to the moving direction of the supplying means, and behind the supplying means in the moving direction of the supplying means. A screen printing apparatus comprising: a mask receiving surface that includes a mask receiving surface that is positioned and moves in synchronization with the supply unit. The screen printing apparatus according to claim 1, wherein the mask receiving surface is located at substantially the same position as the pulling-up means in the moving direction of the supplying means. The screen printing apparatus according to claim 1, wherein the mask receiving surface is made of a soft material and has a curved surface. The screen printing apparatus according to claim 1, wherein a length of the lifting means is equal to or larger than a size of the printing area. 6. The screen printing apparatus according to claim 1, wherein the pulling means is a magnetic force generating means, and the mask has soft magnetism. In a screen printing method for printing a printing material in a predetermined pattern on one surface of a substrate, an elastic mask having an opening corresponding to the pattern is aligned with the substrate, and one end of the mask is pressed while pressing the mask. To the other end to supply the printing material to the opening, pull up the mask after the printing material is supplied to the opening, and receive the mask lifted at a position that is in a fixed relationship with the pressing position of the mask Screen printing method.

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