JP5514624B2 - Screen printing method and apparatus - Google Patents

Description

The present invention relates to a printing method and apparatus for printing a viscous printing material on a printing material using a squeegee through a printing mask having a predetermined opening pattern on the printing material.

 Screen printing is a stencil printing method in which a paste (printing agent) such as ink is squeezed (pushing out the paste (printing agent) with a squeegee) and passed through a screen having an opening pattern to transfer a desired pattern to the printing material. It is used for various purposes such as circuit wiring formation of an IC substrate and FDP (Flat Display Panel) pattern formation (electrode formation and phosphor filling).

  Screen printing is also used, for example, for solder paste printing performed prior to mounting electronic components on a printed circuit board. The solder paste is a cream obtained by mixing solder alloy powder and high-viscosity liquid flux, and is transferred onto a substrate through a printing mask having a predetermined opening pattern. For this screen printing, metal printing masks and metal squeegees that are excellent in terms of mechanical strength and the like are widely used.

  Hereinafter, the current solder printing will be described by referring to a printing mask as a metal screen and a squeegee as a metal squeegee.

  A metal squeegee applies pressure (printing pressure) to the screen surface with solder paste supplied to the surface with its tip inclined at a predetermined attack angle (for example, 70 degrees) with respect to the screen surface of the metal screen. While sliding in the printing direction, the pattern made of the solder paste is transferred onto the printing material through the opening pattern formed on the metal screen.

  Since the printed surface of the printed wiring board introduced into the solder paste printing process has irregularities of about 20 μm to 80 μm due to the solder resist or electrode wiring applied in the previous process, the thickness is about 100 μm made of stainless steel. The metal screen is locally pushed upward by the unevenness of the printed wiring board during printing, and a gap is formed between the metal mask and the printed wiring board. Therefore, when the metal squeegee passes through the convex portion of the metal screen raised by the convex portion of the printed surface of the printed wiring board, a gap is generated between them, which causes a printing defect.

  In order to prevent this, the gap is suppressed to be small by performing printing while applying a large printing pressure to the metal squeegee. For this reason, conventional metal squeegees are made of special steel (super hard alloy) with excellent wear resistance to enhance its durability. Further, as a solution to these problems, Japanese Patent Laid-Open No. 10-100374 (Patent Document 1) discloses that a tapered surface is formed by etching at the tip opposite to the printing direction of the metal squeegee to facilitate elastic deformation. It is described that stable printing is possible even with a small printing pressure, and damage to the screen surface of the metal screen is reduced.

  In Japanese Patent Laid-Open No. 6-281029 (Patent Document 2), in order to minimize friction when sliding with the screen surface, the tip of the squeegee is rounded (in a cross-section arc shape) to form a screen surface. There is disclosed a metal squeegee that can reduce the contact area, perform stable printing, and prevent the screen surface from being easily damaged. However, although the manufacturing method is not described in the above publication, it is considered that the tip of the squeegee is formed round by mechanical polishing or the like by post-processing.

  A printing method using a resin squeegee instead of a metal squeegee is employed as a solution to printing defects due to the level difference of the substrate and a damage reduction measure for the metal screen.

  Hereinafter, screen printing using a resin squeegee will be described by referring to a printing mask as a mesh screen and a squeegee as a urethane squeegee.

  Conventional urethane squeegees include flat squeegees, square squeegees, and sword squeegees. For example, as a conventional example, a rubber-like elastic body described in Japanese Patent Publication No. 1-012755 (Patent Document 3) can be cited.

  As a method for stabilizing the attack angle which is a problem with a flat squeegee, as described in Japanese Utility Model Laid-Open No. 3-055230 (Patent Document 4), it is made of a urethane rubber having a glass epoxy resin as a support. A squeegee has been proposed. The squeegee includes a support body having a base end portion attached to the holder, and a squeegee portion that is integrally fixed so as to cover the front end portion at a front end portion facing the base end portion of the support body. The material of the support is made of glass epoxy resin having elastic restoring force, and the shape is flat.

  The material of the squeegee portion is made of urethane rubber, and a groove portion is provided in the width direction at the other end portion of the squeegee facing the squeegee tip portion to be squeezed, so that the tip portion of the support body is sandwiched. In this way, they are fixed together.

  According to this conventional example, the screen surface can be squeezed by using the squeegee having such a configuration and fixing the squeegee to the holder on the base end side. At this time, when squeezing for a long time, even if the tip of the squeegee changes (swells) due to the solvent of the ink, the support is made of glass epoxy resin. Lumbar strength does not change and can be squeezed stably.

  In addition, as a measure for improving the squeegee made of urethane rubber using a glass epoxy resin as a support, there is a squeegee capable of forming a tapered portion over the side and bottom of the squeegee portion by giving the squeegee portion sufficient thickness. Japanese Patent Laid-Open No. 2005-319816 (Patent Document 5).

  According to this conventional example, in order to set the target attack angle, the taper portion can be formed by performing angle polishing processing on the side surface and the bottom portion of the squeegee portion. Therefore, a desired attack angle can be realized without adjusting the angle by attaching the squeegee to the printing apparatus.

  Furthermore, the Micro Tech Co., Ltd. homepage (Non-patent Document 1) discloses a squeegee (micro squeegee: registered trademark) in which an R-shaped polishing process is applied to the side and bottom of the squeegee portion. Although the attack angle between the squeegee and the printing surface is the same, by processing the tip of the squeegee into an R shape, an effect of preventing the paste from rising to the side of the squeegee during printing can be expected.

  As a metal mask used for screen printing, a metal plate is arranged in a space in a printing mask plate frame, and the metal plate is a tension mesh provided over the entire circumference between the metal plate and the printing mask plate frame. There is a combination mesh type that is supported by the printing mask plate frame in a tensioned state.

  This printing mask is used for screen printing by making a printing mask having a predetermined pattern opening in an effective printing area corresponding to a moving area of a squeegee moved on the metal plate. is there.

  By making the upper surface of the printed material face the lower surface of the metal mask, sliding the squeegee on the upper surface of the metal mask, filling the opening provided in the metal mask with the paste, and then separating the printed material from the metal mask. Used to transfer printing material onto a substrate.

  In the metal plate, an opening having a predetermined pattern is formed in the effective printing area by laser processing, plating, etching, or the like.

  For example, in the etching method, a photoresist is applied on both sides of the metal plate, and the resist film is exposed using an exposure mask having a predetermined pattern and then etched.

  Screen printing methods include, for example, electronic devices, printing of electrode wiring on a printed wiring board, printing of a frame-shaped sealing material on a liquid crystal display substrate, a dielectric layer on a plasma display substrate, pixel spacing walls and electrodes. It is used for various printing such as wiring and fluorescent material printing. The size of the mesh mask, that is, the area of the screen mesh, the size of the printing mask plate frame, the width of the tension mesh, etc. is designed according to the application. Has been.

Japanese Patent Laid-Open No. 10-100430 Japanese Patent Laid-Open No. 6-210829 Japanese Examined Patent Publication No. 1-01275 Japanese Utility Model Publication No. 3-055230 JP 2005-31816 A

Micro Tech Co., Ltd. website: http://www.e-microtec.co.jp/product/index.html

  By the way, with the recent miniaturization of surface mount components, the area of the pad of the printed wiring board has been reduced, and accordingly, the area of the opening of the print mask has also been reduced.

  As described above, the squeegee disclosed in Patent Document 1, that is, the metal squeegee in which the tapered surface is formed by etching with respect to the opening having a small opening surface property, lacks the force to push the solder paste into the opening of the printing mask. Therefore, the adhesiveness between the pad of the printed wiring board and the solder paste in the opening becomes insufficient. As a result, the solder paste remains in the opening of the printing mask, and the solder paste is printed on the pad of the printed wiring board ( There may be a problem that the transfer cannot be performed or the amount of printed paste is insufficient.

  Generally, a metal squeegee has a weaker force to push a solder paste into an opening portion of a print mask than a rubber squeegee made of urethane, and is considered to have caused the above-described problems.

  In general, the tip of the metal squeegee is required to have a high degree of flatness and flatness. However, the conventional metal squeegee described above includes the material (raw material) and the tip of the squeegee. However, there is a problem that the cost is very high. Furthermore, the tip of the squeegee is subjected to a coating treatment such as polytetrafluoroethylene widely known as Teflon (registered trademark) in order to reduce frictional resistance and perform stable printing. In addition, it is a cause of the high cost of metal squeegees.

  Further, the screen surface of the metal screen that is subjected to the sliding contact action with a high printing pressure by the metal squeegee made of cemented carbide has a large damage, particularly in the protrusion raised from the printed wiring board side as described above. . That is, there is a problem that damage on the metal screen side is large in order to perform stable printing using a conventional metal squeegee.

  In general, the squeegee includes a squeegee portion and a holder attaching portion attached to the squeegee holder. The squeegee holder fixes the squeegee by attaching the holder attachment portion of the squeegee. The squeegee holder has a predetermined angle with respect to the printing surface. The attachment angle of the squeegee holder to the printer base can be adjusted to a desired angle.

  The squeegee unit is controlled to move along the surface of the screen mesh at a speed suitable for screen printing while applying a printing pressure suitable for screen printing to the screen mesh. Printing pressure is applied to the point where the squeegee portion and the screen mesh abut. At the point where the squeegee portion and the screen mesh abut, the screen mesh is pushed down toward the surface of the printing material, and an image of the opening pattern formed on the screen is printed on the surface of the printing material. For this reason, in order to perform high-quality printing, it is important that the screen mesh is stretched evenly in a balanced manner on the screen frame and tensioned. The squeegee and the screen are preferably in line contact. Further, it is desirable that the contact line is a straight line.

  The squeegee is in contact with the printing surface at a certain angle, and printing pressure is applied to the printing surface. For this reason, there is a problem in that the angle between the squeegee and the printing surface (referred to as the attack angle) cannot be maintained at a constant angle because the tip of the squeegee is bent. That is, the conventional flat squeegee has a problem that the attack angle changes during printing. However, when the substrate (for example, the above-described printed wiring board) has irregularities, there is an advantage that the irregularities follow the irregularities due to the flat squeegee.

  In a conventional flat squeegee, the entire squeegee part has uniform elasticity, and there is no low back force. Therefore, the shape of the squeegee is stabilized by using metal for the holder mounting part attached to the printing device. Was kept. Further, since the entire squeegee portion has uniform elasticity, there is a drawback that it is difficult to keep the attack angle constant.

  In addition, the conventional square squeegee and sword squeegee cannot be mechanically polished, and there is a problem that it is difficult to obtain linearity between the printing surface and the contact surface of the squeegee.

  Further, in the squeegee described in Patent Document 4 and Patent Document 5, that is, a squeegee made of urethane rubber using a glass epoxy resin as a support, it is possible to suppress the overall bending that is a problem with a flat squeegee. However, since the solder paste rises on the side of the squeegee during printing, the force to push the solder paste into the opening of the printing mask is insufficient, and the adhesiveness between the pad of the printed wiring board and the solder paste in the opening is insufficient As a result, the solder paste remains in the opening of the printing mask, and there may be a problem that the solder paste cannot be printed (transferred) on the pad of the printed wiring board or the amount of the printed paste is insufficient. is there.

  Generally, screen printing using a mesh mask differs from screen printing using a metal mask, and requires a paste coating with a scraper on the printing mask (screen surface side) before printing with a squeegee. That is, the paste can be coated and retained using the mesh present in the opening of the print mask (mesh mask), and the amount of paste discharged can be increased during printing with a squeegee. Conversely, the metal mask cannot coat the print mask with a paste because there is no member to be held in the pattern opening.

  When a metal mask is used, printing is completed in one direction, so that the time required for printing can be shortened compared to a mesh mask that requires a paste coating.

  The mesh mask is provided with a clearance (gap) between the printing mask and the printing material, and can release the plate almost simultaneously with printing.

  On the other hand, since the metal mask does not provide a clearance (gap) between the printing mask and the substrate to be printed, a plate separation step (step of separating the printing mask and the substrate) after printing is required.

  Therefore, even if a mesh mask is used, it is important to complete printing by a one-way operation as in the case of a metal mask. For this purpose, a structure capable of simultaneously satisfying the coating function of the paste for improving the filling property to the opening pattern of the printing mask and the printing function for transferring from the printing mask to the printing material at the tip of the squeegee is provided. This is a problem.

  In general, since paste has improved fluidity when shear (shearing force) is applied, rolling reduces viscosity and improves fluidity. At the same time as printing using a squeegee, improving the rolling property of the paste and improving the printability (fillability / transferability) is also an issue.

  Furthermore, when the paste is printed using a squeegee, the paste rises along the side of the squeegee opposite to the print mask, so that the paste in the print mask is insufficiently filled.

  The problem is to find the structure of the squeegee tip that has the features that can solve such problems.

  In addition, since the paste is filled into the opening pattern formed in the printing mask by the tip of the squeegee, the shape of the tip of the squeegee affects the paste filling property to the printing mask, so that the filling ability is improved. A squeegee tip structure that can be improved over the squeegee is a problem. In particular, since the direction of the force applied to the paste changes depending on the attack angle between the tip of the squeegee and the printing surface of the printing material, it is a problem to fill the opening pattern formed in the printing mask from the substantially vertical direction.

  On the other hand, since the load by printing pressure is added to a squeegee, a front-end | tip part deform | transforms. As described above, since a flat squeegee made of urethane is generally bent, the attack angle at the tip of the squeegee becomes very small, and the attack angle varies depending on the level difference of the substrate. When the attack angle varies, the filling property to the opening portion of the printing mask changes, so that it is a problem to reduce the variation in filling property.

  Depending on the object to be printed, a metal mask, a mesh mask, or the like may be used as a print mask. It is a problem to provide a printing apparatus that can cope with any printing mask. Moreover, as a printing mask, it is a subject to stably transfer a desired amount of paste onto a substrate.

  Furthermore, the paste used varies depending on the printing object. Paste is a high-viscosity material that is a mixture of solids and liquids. Depending on the purpose, the solids are coated with solder composition particles, silver particles, flaky silver particles, nickel-based particles, and metal. It is an object to provide a printing apparatus that can use a paste mainly composed of at least one material selected from resin particles, ceramic particles, and glass particles.

  The present invention has been made in view of the above-described problems, and is capable of mounting a squeegee capable of accurately and stably printing a solder paste on a pad of a printed wiring board regardless of the size of the opening area of the opening of the printing mask. To provide an apparatus. That is, according to the present invention, when filling and transferring a paste into a printing mask having a desired opening, the paste rolling is promoted, the filling property of the paste into the opening of the printing mask is promoted, and the printing mask is applied to the paste. A squeegee tip is processed so that a force is applied in a vertical direction to the opening of the squeegee, and a printing method and apparatus capable of mounting the squeegee are provided.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The squeegee is attached to the case where the squeegee is inclined in the direction opposite to the printing direction and the case where the squeegee is inclined in the printing direction. When the squeegee is inclined in the direction opposite to the printing direction, the direction of the squeegee surface where the paste contacts and the squeegee mounting angle are substantially perpendicular. On the other hand, when the squeegee is inclined in the printing direction, the direction of the squeegee surface where the paste contacts and the squeegee mounting angle are substantially the same.

  Regardless of the method of attaching the squeegee, in a printing apparatus that uses a squeegee to transfer a paste from a printing mask having an opening at a predetermined position to a predetermined position of a substrate fixed on a table, The corner has an arcuate concave shape, and is characterized in that the attack angle between the squeegee and the printing surface of the substrate is smaller than the squeegee mounting angle.

  As a result, the paste is confined in the arc-shaped concave portion at the tip of the squeegee, and the paste is squeezed in the process of squeezing (the squeegee slides in the printing direction while applying pressure (printing pressure) to the screen surface of the printing mask). It is possible to roll along the arcuate concave shape at the tip.

  If the mounting angle of the squeegee is reduced in order to reduce the attack angle, the housing of the squeegee head that applies the printing pressure and the location where the tip of the squeegee contacts the print mask will be displaced relative to each other. It will not be applied effectively to the tip. That is, when a relative displacement occurs in the force point, a rotational moment works. In this case, the higher the printing pressure, the more the squeegee tip has a force in the direction opposite to the printing pressure.

  Therefore, the contact point between the direction in which the printing pressure is applied to the squeegee head and the printing mask at the tip of the squeegee is preferably in the same direction.

  With one of the arcuate concave shapes at the tip of the squeegee in contact with the printing mask, the gap between the arcuate concave shape at the tip of the squeegee and the printing mask is at least 10 times the average particle size of the paste used, and 1 mm It is characterized by the following. The other of the arcuate concave shapes at the tip of the squeegee means a tip that is a concave shape processed into an arc shape at the tip of the squeegee and is not in contact with the printing mask.

  The gap between the tip and the printing mask is related to the size of solid particles contained in the paste used. When the squeegee comes into contact with the print mask, the squeegee may not only fill the opening of the print mask with the paste, but also discharge the print mask toward the substrate. Thereafter, since the tip of the squeegee that originally contributes to printing reaches the opening of the printing mask, a situation in which printing is performed twice is created.

  Similarly to the filling of the paste in the opening pattern portion of the printing mask, the opening pattern portion needs to be at least 10 times larger than the particle size of the solid content in the paste. If the opening pattern portion is smaller than that, the fluidity of the paste will be hindered, and the opening pattern portion will be clogged with particles in the paste, making it impossible to permeate the paste well. Therefore, the gap between the squeegee and the printing mask needs to be at least 10 times the average particle size of the paste used.

  On the other hand, if the clearance between the squeegee and the printing mask is 1 mm or more, the paste cannot be confined in the arc-shaped concave part at the tip of the squeegee, and the pressure applied to the paste is released, filling the opening pattern part of the printing mask. Cause weakening of the power to do. For this reason, the gap between the squeegee and the printing mask is desirably 1 mm or less.

  The smaller the gap between the squeegee and the print mask, the greater the force applied to the paste, and the fillability of the print mask in the opening pattern portion is improved.

  By processing the tip of the squeegee in contact with the print mask into a special shape in this way, the paste is coated on the print mask to a predetermined thickness, the paste is rolled, and the paste is opened in the print mask. It is possible to have a function of filling the part.

  Here, the material of the squeegee used is a resin whose main component is urethane, and its hardness is 80 degrees or more. If the hardness is low, even if a support that suppresses deformation of the squeegee is used as a support, the tip of the squeegee is deformed by the printing pressure during printing, and the attack angle between the squeegee and the printing surface becomes unstable.

  Metal squeegees can be made with extremely high hardness, but the printed surface of the printed wiring board has irregularities formed by solder resist, electrode wiring, etc. applied in the previous process. Flexibility is required at the tip.

  In the printing method and apparatus of the present invention, a printing mask (metal mask) having a metal plate having a predetermined opening can be used as a printing mask. A printing mask characterized by having an organic layer on the surface to be printed can be used.

  Furthermore, in the printing method and apparatus of the present invention, the printing mask (mesh) is characterized in that the pattern forming area is composed of at least a metal mesh and an organic emulsion, and the emulsion has a predetermined opening. Mask) can be used.

  The printing mask used in the printing method and apparatus of the present invention is not limited to the metal mask and mesh mask described here.

  According to the printing method and apparatus of the present invention, the paste can be printed accurately and stably regardless of the size of the opening area of the opening of the printing mask.

1 is a block diagram illustrating a schematic configuration of a printing apparatus according to a first embodiment. FIG. 3 is a flowchart illustrating a flow of processing for performing screen printing in the printing apparatus according to the first exemplary embodiment. FIG. 3 is a side view of the squeegee mechanism showing a schematic configuration of the squeegee mechanism mounted on the printing apparatus according to the first embodiment. FIG. 6 is a diagram for explaining the movement of the squeegee relative to the mask and the state of the solder paste flow at the tip of the squeegee when screen printing is performed by the squeegee mechanism installed in the printing apparatus of the first embodiment. FIG. 5 is a diagram illustrating a state of a solder paste flow at a squeegee tip when screen printing is performed by a squeegee mechanism mounted on the printing apparatus according to the first exemplary embodiment. 1 is a side view of a squeegee mechanism showing a schematic configuration of a pair of squeegee mechanisms used in Embodiment 1. FIG. It is an enlarged view of the front-end | tip part of the squeegee mechanism used for Example 1. FIG. 3 is a schematic diagram of various squeegee tip shapes used in evaluation experiments in Example 1. FIG. It is a side view of a squeegee mechanism showing a schematic configuration of a squeegee mechanism used in Example 3. It is a principal part enlarged view of the squeegee structure explaining a front-end | tip shape. It is the schematic of various squeegee tip shapes used for evaluation experiment in Example 3. It is an enlarged view of the front-end | tip part of the squeegee mechanism used for Example 3. FIG.

In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof is omitted in principle. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The configuration of the printing apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a front view of a printing apparatus 100 according to the first embodiment. In FIG. 1, for the sake of simplification, the display of the frame, side wall, column, support member, and the like of the apparatus is omitted.

  The printing apparatus 100 includes a printing mask unit 110, a substrate support table unit 23, a pair of squeegee units 120L and 120R, a squeegee driving mechanism unit 130, and a control unit 21.

The print mask portion 110 is in a tension state with a metal mask 11 provided with a pattern opening formed corresponding to a desired circuit pattern of a substrate (for example, a printed wiring board) 6 and a tension mesh surrounding the metal mask 11. A plate frame 22 having a rectangular shape in a plan view and a support member 111 that supports the plate frame. The substrate support table unit 23 includes a table 231 on which the substrate 6 is placed, a chuck unit 232 that fixes the substrate 6 placed on the table 231, and a vertical drive unit 233 that drives the table 231 up and down. .
The squeegee unit 120L includes a squeegee 1L, a squeegee holder 3L, a squeegee holder fixing jig 16L, and a squeegee head 15L air cylinder 24L. Similarly, the squeegee portion 120R includes a squeegee 1R, a squeegee holder 3R, a squeegee holder fixing jig 16R, a squeegee head 15R, and an air cylinder 24R. The air cylinders 24L and 24R are fixed to the support member 25, and drive the squeegee portion 120L and the squeegee portion 120R connected to the air cylinders 24L and 24R, respectively, up and down. The support member 25 is supported by bearings 26L and 26R engaged with the drive shaft 27.

  The drive shaft 27 is constituted by a ball screw, and when it is rotationally driven by the motor 30, the bearing portions 26L and 26R engaged with the drive shaft 27 move in the left-right direction in the drawing, and the squeegee portion 120L and the squeegee portion 120R. Moves along the guide shaft 28 in the horizontal direction in the figure. The drive shaft 27 and the guide shaft 28 are supported by a pair of left and right fixing plates 29L and 29R.

  The control unit 21 controls the operation of each unit of the printing apparatus 100. First, the air cylinder drive unit 31 that drives the pair of air cylinders 24L and 24R is controlled by a control signal from the control unit 21 to drive the pair of air cylinders 24L and 24R, respectively. Further, the control unit 21 controls the driver unit 32 of the motor 30 to rotate the motor 30 in the forward and reverse directions. Further, the chuck drive unit 34 that drives the chuck unit 232 of the substrate support table unit 23 is controlled by the control signal from the control unit 21 to open and close the chuck unit 232 that fixes the substrate 6 placed on the table 231. Let the action take place. Furthermore, the table drive unit 33 that drives the vertical drive unit 233 of the substrate support table unit 23 is controlled by a control signal from the control unit 21 to move the table 231 up and down. Furthermore, the chuck 232 is opened and closed by controlling the drive unit 34 of the chuck 232 of the substrate support table unit 23 according to a control signal from the control unit 21.

  The operation of the printing apparatus having the above configuration will be described with reference to the flowchart of FIG. First, the substrate 6 is conveyed by a conveying means (not shown) and placed on the substrate support table 23 (S201), and the substrate 6 is fixed and held on the substrate support table 23 by the chuck portion 232. . Next, the table driving unit 32 drives the vertical driving unit 233 to raise the table 231 (S202), and the substrate 6 is brought into close contact with the metal mask 11 of the printing mask unit 110. Next, the air cylinder 24L is driven by the air cylinder drive unit 31 to lower the squeegee head 15L (S203), and the squeegee 1L is brought into close contact with the metal mask 11 (S204). At this time, the pair of squeegee portions 120L and 120R are located at the left end portion of FIG.

  Next, in this state, solder paste is supplied to the vicinity of the squeegee 1L by a solder paste supply means (not shown) (S205). When the solder paste is supplied, the driver unit 32 is controlled to drive the motor 30, and the drive shaft 27 formed of a ball screw is rotated, thereby making a pair of squeegee units 120L and 120R and a squeegee 1L attached to the tip thereof. The pattern of the metal mask 11 made of solder paste is printed on the substrate 6 by moving from the left side to the right side of FIG. 1 along the metal mask 11 while being pressed against the metal mask 11 (S206).

  After the squeegee 1L has moved a predetermined distance, the driver unit 32 stops driving the motor 30 and stops the movement of the squeegee 1L. Next, the air cylinder drive unit 31 drives the air cylinder 24L to raise the squeegee head 15L (S207), and the squeegee 1L is pulled away from the metal mask 11. Next, the table drive unit 33 controls the vertical drive unit 233 to lower the table 231 (S208), and the substrate 6 held by the chuck unit 232 is peeled off from the metal mask 11.

  When the table 231 reaches the descending end, the processing of the table 231 by the vertical drive unit 233 is stopped, the chuck drive unit 34 is controlled to open the chuck unit 232 holding the substrate 6 and handling means (not shown) Thus, the substrate 6 is removed from the table 231 (S209). It is determined whether or not the substrate thus taken out is the last substrate to be processed (S210). In the last case, the processing is terminated.

On the other hand, if there is a substrate to be processed next, the processing flow from S201 is executed again. However, in this case, the squeegee head 15R is lowered in S203, and the squeegee 1L is replaced with 1R in S204, S206, and S207. Further, screen printing is performed by moving the squeegee 1R in close contact with the metal mask 11 from the right side to the left side in FIG. Thus, the solder paste supplied by performing screen printing using the squeegees 1L and 1R alternately is always in front of the traveling direction of the squeegee that is in close contact with the metal mask. Can be used effectively.
Next, some specific examples of the configuration of the pair of squeegee units 120L and 120R will be described.

First, a first example of the structure of the squeegee unit 120L will be described with reference to FIG. 3A. The structure of the squeegee unit 120R is basically the same as that of the squeegee unit 120L. The squeegee 1L is fixed to the squeegee holder 3L by the squeegee holder pressing plate 4L so as to incline in the opposite direction to the printing direction 2. The squeegee holder 3L supports the squeegee 1L at a predetermined angle with respect to the printing mask surface 5, the printing surface of the substrate 6, or the substrate support surface (upper surface) of the substrate support table (231 in FIG. 1). A squeegee mounting surface 7L is provided. In the squeegee 1L, an arcuate concave portion 8L is formed at a corner of the squeegee 1L that is in contact with the printing mask (metal mask) 11 at the tip.
When printing, the solder paste 9 first contacts the squeegee paste initial contact surface 10L, which is essentially perpendicular to the angle of the mounting surface 7L of the squeegee 1L, and simultaneously coats the solder paste 9 on the metal mask 11, Solder paste 9 is inserted into the printing mask opening 12 formed in the metal mask 11. Further, the solder paste 9 rolls at the arc-shaped concave portion 8L at the tip of the squeegee and solders until reaching the electrode pad 13 on the substrate 6 through the pattern opening 12 of the printing mask formed on the metal mask 11. Paste 9 is filled. The printed material 6 is covered with a solder resist 14 other than the predetermined pattern opening of the electrode pad 13.

  The solder paste 9 rolls at the arcuate concave portion 8L at the tip of the squeegee 1L and reaches the electrode pad 14 on the substrate 6 through the pattern opening 12 of the printing mask with reference to FIGS. 3B and 3C. This will be described in detail.

  First, using FIG. 3B, when the squeegee 1L is moved in the direction of the arrow 2 while pressing the squeegee 1L against the metal mask 11, the solder paste 9 is formed on the metal mask 11 from the arc-shaped concave portion 8L at the tip of the squeegee. The manner of filling the electrode pads 13 on the substrate 6 through the pattern openings 12 of the printing mask will be schematically described in the order of time series (a) to (e).

  (A) shows a state before the arcuate concave portion 8L at the tip of the squeegee 1L reaches the pattern opening 12 of the printing mask formed on the metal mask 11 yet. When the corner 81L at the tip of the squeegee 1L is pressed against the surface 5 of the metal mask 11 and moves in the direction of the arrow 2, the solder paste 9 supplied to the front surface in the direction of travel of the squeegee 1L is the initial paste contact of the squeegee 1L. It is pushed by the surface 10L and moves in the same direction as the squeegee 1L, and a part of the arcuate recess is formed from the gap G between the corner 82L of the arcuate concave portion 8L at the tip of the squeegee 1L and the metal mask 11. It enters the inside of the shape portion 8L (A), hits the corner portion 81L of the tip of the squeegee 1L pressed against the surface 5 of the metal mask 11 and escapes upward (b), and further the arc-shaped concave shape portion 8L Extruded from the gap G along the upper surface to the paste initial contact surface 10L side of the squeegee 1L (C).

  As the squeegee 1L further advances in the direction of the arrow, the corner 82L of the arcuate concave portion 8L at the tip of the squeegee 1L is above the pattern opening 12 of the printing mask formed in the metal mask 11 as shown in FIG. Is reached, a part of the solder paste that has been extruded from the gap G toward the paste initial contact surface 10L side of the squeegee 1L along the upper surface of the arc-shaped concave portion 8L is pushed into the pattern opening 12 of the printing mask. (D).

When the squeegee 1L further advances in the direction of the arrow and the arcuate concave portion 8L at the tip of the squeegee 1L reaches above the pattern opening 12 of the printing mask formed on the metal mask 11 as shown in FIG. The pressing force no longer acts on the pattern opening 12 of the printing mask, and the gap between the corner 82L of the arcuate concave shape 8L at the tip of the squeegee 1L and the metal mask 11 is the same as in the state of (a). The solder paste 9 that has entered the inside of the arc-shaped concave portion 8L from the gap G is extruded from the gap G to the paste initial contact surface 10L side of the squeegee 1L along the upper surface of the arc-shaped concave portion 8L ( C).
As the squeegee 1L further advances in the direction of the arrow, the corner 81L of the arc-shaped concave portion 8L at the tip of the squeegee 1L pressed against the metal mask 11 as shown in (d) is above the pattern opening 12 of the printing mask. When it reaches, a part of the solder paste that hits the corner 81L inside the arc-shaped concave portion 8L is pushed into the pattern opening 12 of the printing mask (e), and the rest escapes upward (b), Extruded from the gap G toward the paste initial contact surface 10L side of the squeegee 1L along the upper surface of the arc-shaped concave portion 8L (C).

  When the squeegee 1L further advances in the direction of the arrow and the corner 81L of the arc-shaped concave portion 8L at the tip of the squeegee 1L passes the pattern opening 12 of the printing mask as shown in (d), screen printing by the pattern opening 12 is performed. Ends.

  Here, in FIG. 3B (b), a state in which the solder paste rolls inside the arc-shaped concave portion 8L and a part thereof is pushed into the pattern opening 12 of the print mask will be further described with reference to FIG. 3C. explain in detail.

  In FIG. 3C, a change in the position of the solder paste 9 relative to the squeegee 1L in the arc-shaped concave portion 8L at the tip of the squeegee 1L is indicated by an arrow. In FIG. 3C, (A) to (G) attached to the arrow indicating the movement of the solder paste 9 are not directly related to (A) to (E) described in FIG. 3B.

  When the edge 81L at the lower end of the squeegee 1L is pressed against the metal mask 11 and is driven by the squeegee driving mechanism 130 and proceeds in the direction of arrow 2, the solder paste 9 supplied to the front of the squeegee 1L is (a) The recess 8L formed in the squeegee 1L enters the inside of the recess 8L through the gap G between the end 82L opposite to the side in contact with the metal mask 11 and the metal mask 11 (b).

  When the squeegee 1L further advances in the direction of arrow 2, the solder paste 9 that has entered the recess 8L is pushed upward at the end 81L because the end 81L of the recess 8L is in contact with the metal mask 11 (ha ), Pushed back in the opposite direction (d). When the squeegee 1L further advances in the direction of the arrow 2, the solder paste 9 flows downward (e) in the direction of the end 82L along the wall surface of the recess 8L, and further flows downward at the tip of the end 82L. The portion is pushed into the opening 12 formed in the metal mask 11 (f), and the inside of the opening 12 is filled with the solder paste 9 and connected to the electrode pad 13 on the substrate 6.

  The solder paste 9 that could not enter the opening 12 is discharged from the gap G between the end portion 82L and the metal mask 11 to the paste initial contact surface 10L side of the squeegee (g). That is, the solder paste 9 that has entered the inside of the recess 8L rolls inside the recess 8L and is discharged again to the outside of the recess 8L.

  Thus, when the squeegee 1L advances in the direction of arrow 2, the solder paste 9 that has entered the recess 8L from the gap G between the end 82L of the recess 8L formed in the squeegee 1L and the metal mask 11 is When the inside of the recess 8L rolls and is discharged to the outside of the recess 8L from the gap G between the end 82L and the metal mask 11, a part of the inside of the opening 12 formed in the metal mask 11 As a result, the solder paste is reliably filled into the opening 12.

  The printing mask 110 used for printing arranges the metal plate 11 in the space in the printing mask plate frame 22, and the metal plate 11 is disposed between the metal plate 11 and the printing mask plate frame 22 over the entire circumference. It is a combination mesh type supported by the printing mask plate frame 22 in a tensioned state via a tension mesh (not shown) provided.

  The printing mask 110 is used for printing by forming a predetermined pattern of openings 12 in the effective printing area corresponding to the moving area of the squeegee 1L moved on the metal plate 11, and making a plate. It is.

  A squeegee mechanism mounted on the printing apparatus 100 according to the first embodiment will be described with reference to FIG. As described with reference to FIG. 3A, the squeegee holder 3L to which the squeegee 1L is fixed is fixed to the squeegee head 15L and is installed so that the other squeegee head 15R forming a pair that moves independently faces each other. The squeegee heads 15L and 15R set angles using squeegee holder mounting angle setting jigs 20L and 20R in order to obtain a predetermined attack angle between the surface 5 of the metal mask 11 and the squeegees 1L and 1R. 3L and 3R are fixed by squeegee holder fixing jigs 16L and 16R.

  The squeegee tip structure mounted on the printing apparatus 100 of the first embodiment will be described with reference to FIG. 5 taking the squeegee 1L as an example. The squeegee 1L is attached to the squeegee holder 3L (see FIG. 3) at an attachment angle 17 (an angle with respect to the horizontal direction). In the first embodiment, the attachment angle 17 of the squeegee 1L to the squeegee holder 3L is 35 °. At the tip of the squeegee 1L, an arcuate concave portion 8L is formed at a corner 81 in contact with the printing mask 11. This arc-shaped concave portion 8L is the other end of the arc-shaped concave portion 8L when the corner portion 81 is brought into contact with the printing mask 11 with the squeegee 1L being attached to the squeegee holder 3L at the attachment angle 17L. A gap G is formed between 82L and the surface 5 of the printing mask 11.

As described with reference to FIGS. 3B and 3C, the solder paste 9 rolled inside the arc-shaped concave portion 8 </ b> L is between the other end 82 </ b> L of the arc-shaped concave portion 8 </ b> L and the surface 5 of the printing mask 11. In order to generate a pressing force against the squeegee 1L when it is discharged to the solder paste initial contact surface 10L side of the squeegee 1L through the gap G, it is necessary to create a downward flow in the solder paste 9 when passing through the gap G There is. For this purpose, as a condition of the other end 82L of the arc-shaped concave portion 8L, the angle θ _L of the tangent of the arc-shaped concave portion 8L at the other end 82L shown in FIG. 5B with respect to the surface 5 of the metal mask 11 is 5 What is necessary is just to form the arc-shaped concave shape part 8L so that it may become the value of the range of 80 to 80 degree | times.
The initial contact surface 10L of the squeegee, which is essentially perpendicular to the angle 17L of the squeegee 1L attached to the squeegee holder 3L, the printing mask surface 5 (squeegee contact surface), the printing surface of the substrate 6 or the substrate support table 231. The angle with the substrate 6 support surface is a paste initial contact surface angle 18L. In Example 1, the paste initial contact surface angle 18L is 55 °.

  On the other hand, at a position 81L where the squeegee 1L is in contact with the print mask 11, the angle between the squeegee 1L and the squeegee contact surface of the print mask surface 5 is an attack angle 19L. In the first embodiment, the printing state is verified by swinging the attack angle 19L.

The solder paste 9 can be inserted into the pattern opening 12 formed in the printing mask 11 at the same time as the solder paste 9 is coated on the surface 5 of the printing mask 11 using the paste initial contact surface angle 18L. Further, the solder paste 9 is forcibly rolled inside the arcuate concave portion 8L at the tip of the squeegee 1L, and a force is applied to the solder paste 9 in a direction perpendicular to the pattern opening 12 formed in the printing mask 11. In addition, the solder paste 9 can be filled until it reaches the electrode pad 13 on the substrate 6 through the pattern opening formed in the printing mask 11 at the attack angle 19L.
A feature of the squeegee 1L of the present embodiment is that the squeegee 1L has an arc-shaped concave portion 8L at the tip, and has an attack angle 19L smaller than the paste initial contact surface angle 18L. It should be noted that the squeegee 1R can have the same effect as that of the squeegee 1L by providing the arc-shaped concave portion 8R at the tip.

  As a solder paste used in the verification experiment of Example 1, (A): LF-204-15 (manufactured by Tamura Chemical Co., Ltd., particle size of solder particles: 1 to 12 μm) and (B): M705-BPS7-T1J (Senju Metal Industry Co., Ltd., solder particle size: 1-6 μm), using a resin squeegee with seletan as the main component, the printing mask 11 and a 70 μm thick metal plate with a diameter of 50 μm— Screen printing was performed using a metal mask having a pattern opening 12 of 200 μm.

The squeegee 1 is inclined in the direction opposite to the printing direction. The squeegee holder is attached at an angle of 35 ° and the paste initial contact surface angle 18 (the angle in the direction of the squeegee surface where the squeegee precedes the paste) is 55. °.
Further, as a squeegee used for verification, a resin mainly composed of urethane was used.

  In the pattern opening 12, the value obtained by dividing the area of the wall surface of the pattern opening 12 by the area of the pattern opening is the print index. That is, it was aimed that the printing index is 2.8 or more and that the solder paste can be satisfactorily transferred.

  As a result of the experiment, when (A) is used as the solder paste, if the gap G between the squeegee tip 82L that does not contact the print mask 11 and the print mask surface 5 becomes smaller than 0.12 mm, the solder paste 9 Was prevented from flowing into the arcuate concave portion 8 formed at the tip of the squeegee, and the amount of solder paste transferred was reduced.

  When (B) is used as the solder paste, when the gap G between the squeegee tip 82 that does not contact the print mask 11 and the print mask surface 5 becomes smaller than 0.06 mm, the solder paste 9 becomes the squeegee tip. The amount of solder paste to be transferred was reduced by inhibiting the fluid from flowing into the arc-shaped concave portion 8 formed in the above.

  On the other hand, if the gap G between the squeegee tip 82L that is not in contact with the print mask 11 and the print mask surface 5 is larger than 1 mm, the solder paste is confined in the arc-shaped concave portion 8 formed at the squeegee tip during printing. Since the force applied to the solder paste 9 filling the pattern opening 12 of the printing mask 11 is weakened, the filling amount and the transfer amount are insufficient.

  As a result of this experiment, in a state where one of the arc-shaped concave portions 8L formed at the tip of the squeegee is in contact with the print mask surface 5, the other 82L of the arc-shaped concave portion 8L at the tip of the squeegee and the print mask surface 5 are obtained. It can be seen that the gap G between and the average particle size of the paste used is 10 times or more and 1 mm or less. The other of the arcuate concave portion 8L at the tip of the squeegee means a tip 82L that is a concave shape processed into an arc shape at the tip of the squeegee and is not in contact with the print mask surface 5.

  Further, as a comparative example, a printing experiment was performed using a squeegee that is not processed at the tip of the squeegee and a squeegee that is subjected to linear oblique polishing as shown in FIG.

  As a result, in the case of using the squeegee that is not processed at the tip portion shown in FIG. 6B, good pattern printing could not be performed unless the diameter of the opening 12 of the pattern was 150 μm or more. In addition, when a squeegee having a processed tip as shown in FIG. 6C was used, good pattern printing could not be performed unless the diameter of the pattern opening 12 was 120 μm or more.

  On the other hand, when printing is performed using a squeegee in which concave shapes are formed on a plurality of surfaces as shown in FIG. 6D, printing is performed using the squeegee in which the cross section of FIG. As a result, almost the same results as those obtained were obtained, and all the patterns of the pattern openings 12 having a diameter of 50 μm to 200 μm formed on the metal mask could be satisfactorily screen-printed.

  As described above, the printing apparatus according to the first embodiment can be equipped with a squeegee that can accurately and stably print the paste regardless of the size of the opening area of the opening of the printing mask 11. For this purpose, by rolling the tip of the squeegee into a special shape, the paste is rolled into the pattern opening 12 of the printing mask 11 having a desired opening, and the paste is transferred to the substrate. In addition to promoting the filling of the paste into the opening 12 of the printing mask 11, it was possible to apply a force for filling the opening 12 of the printing mask 11 in the substantially vertical direction to the paste.

  The second embodiment is the same as the first embodiment except that a mesh mask is used as the print mask 11.

  In the second embodiment, a mesh is used for the print mask 11. As the mesh, # 325 plain weave using a high-strength wire having a wire diameter of 16 μm and a thickness of 35 μm was used. A mesh mask in which a pattern opening having a diameter of 50 μm to 200 μm was formed by using an emulsion having a thickness of 35 μm and a thickness of 55 μm was used for this mesh.

  In order to separate the printing mask 11 from the substrate 6 using mesh tension, the tension of the printing mask was set to 0.2 mm or less (measured with a tension gauge STG-80NA manufactured by Protech Co., Ltd.).

  The metal mesh used for the printing mask 11 used in the second embodiment has an opening ratio of 40% or more, and the wire diameter used for the metal mesh needs to be smaller than half the opening width of the metal mesh.

  In the pattern opening 12 formed in the mesh mask, a value obtained by dividing the area of the wall surface of the pattern opening 12 by the area of the pattern opening is a printing index. That is, the target of the second embodiment is that a good transfer of the solder paste can be performed when the printing index is 2.8 or more.

  In the second embodiment, since there is a gap between the mesh mask and the substrate 6, unlike the contact printing using the metal mask used in the first embodiment, one of the arc-shaped concave portions 8 </ b> L formed at the tip of the squeegee has 81 </ b> L. In a state where the surface of the printing mask 11 is in contact with the surface 5, the mesh mask is inclined rather than horizontal. Therefore, the gap G between the other 82L of the arcuate concave portion 8L at the tip of the squeegee 1L and the print mask surface 5 is reduced.

  The gap G between the other 82L of the arcuate concave shape 8L at the tip of the squeegee and the printing mask surface 5 needs to be 10 times or more the average particle diameter of the paste to be used and 1 mm or less. The other of the arcuate concave shape portion 8 at the tip of the squeegee means the tip portion 82L that is not in contact with the mesh mask in the concave shape portion 8L processed into an arc shape at the tip of the squeegee 1L.

  Since the particle size of the solder particles of the solder paste 9 used in the second embodiment is 12 μm or less as in the first embodiment, the squeegee tip 82 that does not contact the mesh mask and the print mask surface 5 The gap G was 0.6 mm. When the squeegee comes into contact with the mesh mask, it not only fills the mesh mask opening with paste, but also discharges to the substrate side of the mesh mask, and then the tip of the squeegee that originally contributes to printing is the mesh mask opening. When it reached, the situation was printed twice. For this reason, the paste oozes out between the mesh mask and the substrate to be printed, resulting in bleeding.

  When LF-204-15 of (A) is used as the solder paste, if the gap between the tip 82L of the squeegee 1L not in contact with the mesh mask and the printing mask becomes smaller than 0.12 mm, the solder paste 9 Is prevented from flowing into the arcuate concave portion 8L formed at the tip of the squeegee 1L, and the amount of solder paste to be transferred is reduced.

  Further, when M705-BPS7-T1J of (B) is used, when the gap G between the squeegee tip 82L that is not in contact with the mesh mask and the print mask surface 5 becomes narrower than 0.06 mm, the solder paste becomes squeegee. The amount of solder paste to be transferred was reduced by inhibiting the flow into the arcuate concave portion 8 formed at the tip of 1 L.

  On the other hand, if the gap G between the tip portion 82 of the squeegee 1L that is not in contact with the mesh mask and the print mask surface 5 is larger than 1 mm, the solder paste is placed in the arc-shaped concave portion 8L formed at the tip of the squeegee 1L during printing. Since the force applied to the solder paste filling the pattern opening 12 of the mesh mask is weakened, the filling amount and the transfer amount are insufficient.

  The result of verifying the printing status in Example 2 was the same as the result of verifying the printing status in Example 1. That is, all the patterns of the pattern openings 12 having a diameter of 50 μm to 200 μm formed on the mesh mask could be satisfactorily screen printed.

  Thus, the printing apparatus of the second embodiment can be equipped with a squeegee that can print the paste 9 accurately and stably regardless of the size of the opening area of the opening 12 of the print mask 11. For this purpose, by processing the tip of the squeegee into a special shape, the paste 9 is rolled into the pattern opening 12 of the printing mask 11 having a desired opening, and the paste is transferred to the substrate. And the filling property of the paste into the opening 12 of the printing mask 11 can be promoted, and a force for filling the opening 9 of the printing mask 11 in the substantially vertical direction can be applied to the paste 9.

  A squeegee structure mounted on the printing apparatus according to the third embodiment will be described with reference to FIG. As the squeegee used in Example 3, a flat squeegee, a squeegee 71 inserted in the center of the squeegee using a glass epoxy resin plate 727 as a support, was used.

FIG. 8 shows a schematic diagram of the tip shape of the squeegee 71 used in the third embodiment. FIG. 8 shows an enlarged view of the main part of the squeegee structure, taking a flat squeegee as an example in order to explain the tip shape of the squeegee 71.
In the third embodiment, the mounting direction of the squeegee 71 is opposite to that in the first embodiment, and the squeegee 1 is inclined in the same direction as the printing direction 2. Except for changing the shape of the squeegee 71, it is the same as the first embodiment. The configuration of the printing apparatus used in the third embodiment is basically the same as the configuration described with reference to FIG. 1, and the squeegee units 120L and 120R in FIG. 1 are configured as shown in FIG. Since it is a thing replaced with a thing, description of a whole block diagram is abbreviate | omitted.

  In attaching the squeegee, there are a case where the squeegee 1 is inclined in the direction opposite to the printing direction 2 as in the first and second embodiments, and a case where the squeegee 71 is inclined in the printing direction 2 as in the third embodiment. When the squeegee 1 is inclined in the direction opposite to the printing direction 2 as in the first and second embodiments, the surface 10 of the squeegee 1 in contact with the paste 9 and the attachment angle 17 of the squeegee 1 are substantially perpendicular. On the other hand, in the third embodiment, when the squeegee 71 is inclined in the printing direction 2, the direction of the surface 710 of the squeegee 71 with which the paste 9 contacts is substantially the same as the mounting angle 717 of the squeegee 71.

  Also in the present embodiment, in the printing apparatus that uses the squeegee 71 to transfer the paste 9 from the printing mask 11 having the opening 12 at a predetermined position to a predetermined position of the substrate 6, the tip of the squeegee 71 is transferred. One corner of the squeegee has an arcuate concave shape 78, and the attack angle 719 between the squeegee 71 and the printing surface of the substrate 6 is smaller than the attachment angle 718 of the squeegee 71.

Thereby, the paste is confined in the arc-shaped concave shape 78 at the tip of the squeegee 71, and squeezing (the squeegee 71 slides in the printing direction while applying pressure (printing pressure) to the screen surface of the print mask 11). The paste 9 was able to roll along the arcuate concave portion 78 at the tip of the squeegee 71 in the process of.
The squeegee used in Example 3 used a resin mainly composed of urethane.

  As shown in FIG. 9, when the attachment angle 717 of the squeegee 71 is reduced in order to reduce the attack angle 719, a squeegee head 715 for applying printing pressure and a portion 781 where the tip of the squeegee 71 contacts the print mask surface 5 are formed. Since relative displacement occurred, the printing pressure was not effectively applied to the tip of the squeegee 71. That is, when a relative displacement occurs in the force point, a rotational moment works. In this case, the higher the printing pressure, the more the squeegee tip has a force in the direction opposite to the printing pressure.

  Therefore, the contact point 781 between the direction in which the printing pressure is applied to the squeegee head 715 and the print mask surface 5 at the tip of the squeegee 71 is adjusted to be in substantially the same direction.

  In the third embodiment, in a state where one of the arc-shaped concave portions 78 formed at the tip of the squeegee 71 is in contact with the print mask 11, printing is performed with the other 782 of the arc-shaped concave portion 78 at the tip of the squeegee 71. The gap G with the mask surface 5 needs to be 10 times or more the average particle diameter of the paste 9 used and 1 mm or less. The other of the arcuate concave portion 878 at the tip of the squeegee 71 means the tip 782 that is not in contact with the print mask surface 5 by the concave portion 78 processed into an arc shape at the tip of the squeegee 71.

  Since the particle size of the solder particles of the solder paste 9 used in Example 3 is 12 μm or less, the gap G between the squeegee tip 782 that does not contact the print mask 11 and the print mask surface 5 is 0.3 mm. It was. When the squeegee 71 comes into contact with the print mask 11, the squeegee tip not only fills the opening 12 of the print mask 11 but also discharges it to the substrate 6 side of the print mask 11 and then contributes to printing. When the ink reaches the opening 12 of the printing mask 11, the printing is performed twice. For this reason, the paste oozes out between the printing mask 11 and the substrate 6 to cause bleeding.

  When A is used as the solder paste, when the gap G between the squeegee tip 82 that is not in contact with the print mask 11 and the print mask surface 5 becomes smaller than 0.12 mm, the solder paste forms a circle formed at the squeegee tip. The amount of solder paste to be transferred was reduced by inhibiting the flow into the arc-shaped concave portion 8.

  When B is used as the solder paste, when the gap G between the squeegee tip 782 that is not in contact with the print mask 11 and the print mask surface 5 becomes smaller than 0.06 mm, the solder paste 9 is formed at the squeegee tip. The amount of solder paste to be transferred is reduced by preventing the flow into the arc-shaped concave portion 78.

  On the other hand, if the gap G between the tip portion 782 of the squeegee 71 that does not contact the print mask 11 and the print mask surface 5 is larger than 1 mm, the squeegee may be trapped in the arc-shaped concave portion 78 formed at the tip of the squeegee during printing. Since it could not be performed and leaked from the arc-shaped concave portion 78 and the force applied to the solder paste 9 filling the pattern opening 12 of the printing mask 11 was weakened, the filling amount and the transfer amount were insufficient.

  In the third embodiment, as in the first embodiment, a printing mask 11 in which a pattern opening 12 having a diameter of 50 μm to 200 μm is formed on a metal plate having a thickness of 70 μm was used.

  In the third embodiment, the squeegee 71 is inclined in the same direction as the printing direction 2, the attachment angle 717 of the squeegee 71 to the squeegee holder 73 is 70 °, and the paste initial contact surface angle 718 (the squeegee 71 precedes). The angle in the direction of the surface of the squeegee 71 in contact with the paste 9 was set to 70 °, which is substantially the same as the mounting angle 717 to the squeegee holder 73. The angle between the squeegee 71 and the squeegee contact surface of the printing mask 11 was examined by changing the attack angle 719. As for the printing status, the filling property of the printing mask 11 into the pattern opening 12 and the transfer property to the substrate were verified.

  The result of verifying the printing status in Example 3 was the same as the result of verifying the printing status in Example 1.

  As described above, the printing apparatus according to the third embodiment can be equipped with a squeegee that can accurately and stably print the paste regardless of the size of the opening area of the opening 12 of the print mask 11. For this purpose, the tip of the squeegee 71 is processed into a special shape so that the paste is filled into the opening pattern portion 12 of the printing mask 11 having the desired opening 12 and the paste is transferred to the substrate. , The filling ability of the paste into the opening 12 of the printing mask 11 was promoted, and a force for filling the opening 12 of the printing mask 11 in the substantially vertical direction could be applied to the paste.

  In the fourth embodiment, the squeegee mounting direction is opposite to that in the first embodiment, and the squeegee is inclined in the same direction as the printing direction 2. Except for changing the shape of the squeegee, it is the same as the second embodiment.

  The result of verifying the printing status in Example 4 was the same as the result of verifying the printing status in Example 2.

  As described above, the printing apparatus of the fourth embodiment can be equipped with the squeegee 1 that can print the paste accurately and stably regardless of the size of the opening area of the opening 12 of the print mask 11. For this purpose, by processing the tip of the squeegee into a special shape, the paste is rolled into the opening pattern portion 12 of the printing mask 11 having a desired opening, and the paste is transferred to the substrate to be printed. In addition to promoting the filling of the paste into the opening 12 of the printing mask 11, it was possible to apply a force for filling the opening 12 of the printing mask 11 in the substantially vertical direction to the paste.

  Example 5 is the same as Examples 1 to 4 except that various pastes are used.

  In the printing apparatus of the present invention, the paste to be used is a high-viscosity material in which a solid content and a liquid content are mixed, and the solid content is a solder composition particle, silver particle, flake-shaped silver particle, or particle mainly composed of nickel. The main component is at least one material selected from the group consisting of metal-coated spherical resin particles, ceramic particles, and glass particles. The characteristics and printing results of the object to which these pastes are applied are as follows: Shown in

  The paste using the solder composition particles as a solid content is used for surface mounting technology such as pad bumps of a printed wiring board, and formation of solder connection terminals such as pad bumps of a semiconductor wafer. The shape of the solder composition particles used is approximately spherical.

  The particle size of the solder composition particles can be selected according to the pattern used from about 1 μm to about 30 μm. In this case, the size of the opening pattern 12 formed in the printing mask 11 is set to 10 times or more the particle size of the solder composition particles in consideration of the fluidity of the paste in the opening portion. Good printing similar to that of Embodiments 1 to 4 could be performed.

  That is, when the particle size of the solder composition is 1 μm, the size of the opening pattern needs to be 10 μm or more. When the particle size of the solder composition is 30 μm, the size of the opening pattern needs to be 300 μm or more. In order to form a fine pattern, it is necessary to use particles having a fine particle size solder composition.

  A paste using silver particles as a solid content is used for forming a wiring pattern of a low-temperature fired ceramic, forming an electrode of a solar cell, and the like. The shape of the silver particles used is almost spherical.

  The particle diameter of the silver particles is about 2 nm to about 10 μm. When forming a fine wiring pattern, it is necessary to use particles having a fine particle diameter.

  On the other hand, since the silver paste used for electrode formation of solar cells needs to reduce the wiring resistance of the electrode, it is required to form the wiring pattern with a large thickness and to be fired at a low temperature. It is necessary to use a paste in which particles having a particle size and particles having a particle size of several nm are mixed. If the wiring width is 50 μm, the effective particle size of the silver particles used is 5 μm or less. In this embodiment, since the transferability is improved, it is possible to obtain a good printing result with a high aspect ratio of the wiring pattern and capable of handling fine wiring.

  In addition, paste using flaky silver particles as a solid content is a conductive conductive adhesive used when components are mounted on a printed wiring board. Used for mounting. The flaky silver particles are processed into a foil shape by applying pressure to the silver particles, and are irregularly shaped particles. This paste is characterized in that it does not require much transfer dimension accuracy of the printed pattern in order to ensure conductivity with contact resistance, but in this embodiment, since the discharge property can be improved, it is localized. It was possible to print reliably without causing poor coating.

  A paste using particles containing nickel as a main component as a solid content is used for a capacitor or the like that needs to form an ultra-thin conductor. The particle size of the nickel-based particles is about 10 nm to about 100 nm, and is characterized in that the paste has a low viscosity and has fluidity.

  As the heel thickness decreases, the amount of paste retained decreases. When the discharge amount is increased, it is desirable to increase the thickness. On the other hand, for the formation of fine electrode wiring patterns and capacitor thin film electrodes, it is desirable that the thickness is thinner. When it was necessary to make it thinner than the thickness after weaving, a mesh having a desired thickness was used by rolling the mesh with a roll. It was possible to select the type of mesh (number of meshes, aperture ratio, wire diameter, thickness, etc.) depending on the device to be applied.

  In the fifth embodiment, since the discharge property could be improved, uniform and very thin film pattern formation was possible, and good printing results could be obtained.

  On the other hand, paste that uses spherical resin particles coated with metal as a solid content is an anisotropic conductive paste, and parts for printed wiring boards that allow electrical connection even if resistance is higher than that of display terminals and metal joints Used for mounting. The particle diameter of the resin particles coated with metal is about 10 μm, and the print pattern is characterized in that it is applied to the entire pad portion of the component to be mounted. In the present embodiment, since the dischargeability could be improved, local printing failure did not occur, and good printing results could be obtained.

  Pastes that use ceramic particles as solid content include dielectric pattern formation of low-temperature fired ceramics, insulating pattern formation of electronic circuits, pattern formation of resists for etching on copper-clad polyimide films, pattern formation for insulating layer scribing of solar cells, etc. Used for. In this embodiment, since it has a reliable transfer performance, a local disconnection failure does not occur and a good printing result can be obtained.

  Pastes that use glass particles as a solid content are used for addition to silver paste as a sintering aid, dielectric pattern formation of low-temperature fired ceramics, insulating pattern formation of electronic circuits, and the like.

  Ceramic particles and glass particles are crushed because they are produced by pulverization. In these cases, it is necessary to make the opening pattern of the printing mask used 10 times or more the average particle diameter.

  The squeegee 1 used in the fifth embodiment has a concave-shaped portion 8 in which one corner of the squeegee tip has an arcuate shape, and an angle 18 in the direction of the squeegee surface where the squeegee 1 comes into contact with the paste first (printing direction and All these pastes by making the attack angle between the squeegee and the printing surface of the substrate smaller than the squeegee tilted in the opposite direction) or the squeegee mounting angle (when squeegee tilted in the same direction as the printing direction) On the other hand, regardless of the size of the opening area of the pattern opening 12 of the printing mask 11, a printing apparatus capable of printing with high accuracy and stability could be obtained.

  Although the embodiments of the present invention have been described above, various alternatives, modifications, and variations can be made by those skilled in the art based on the above description. It encompasses alternatives, modifications or variations.

  As described above, the printing apparatus according to the fifth embodiment can be equipped with the squeegee 1 that can print the paste accurately and stably regardless of the size of the opening area of the pattern opening 12 of the printing mask 11. . For this purpose, by processing the tip of the squeegee into a special shape, the paste is rolled into the opening pattern portion 12 of the printing mask 11 having a desired opening, and the paste is transferred to the substrate to be printed. In addition to promoting the filling of the paste into the opening 12 of the printing mask 11, it was possible to apply a force for filling the opening 12 of the printing mask 11 in the substantially vertical direction to the paste.

  DESCRIPTION OF SYMBOLS 1,71 ... Squeegee 3, 73 ... Squeegee holder 5 ... Print mask surface 6 ... Printed material 8, 78 ... Arc-shaped concave shape part of squeegee tip 9 ... Solder paste 11 ... Print mask 21 ... Control panel 22 ... Plate frame 23 ... Substrate support table section 100 ... Printing device 110 ... Print mask section 120L, R ... Squeegee section 130 ...・ Squeegee drive mechanism.

Claims (8)

Mask holding means for holding a mask for screen printing;
Table means for placing a sample to be screen printed and moving the sample up and down;
A squeegee means comprising a squeegee for printing a solder paste pattern on the sample placed on the table means via the mask;
A screen printing apparatus comprising squeegee driving means for reciprocating the squeegee of the squeegee means along the mask,
The squeegee of the squeegee means has a first surface and a second surface that are in contact with each other, the first surface being concave, and the concave shape when the squeegee is pressed against the mask . The boundary of the first surface opposite to the boundary that touches each other is in contact with the mask, and the first surface and the second surface are printed more than the position of the boundary of the first surface that contacts the mask. It is formed forward with respect to the direction of movement, and the angle formed by the mask and the boundary portion of the first surface that contacts the mask is greater than the angle formed by the second surface and the mask. The tip of the concave first surface that is small and the boundary between the first surface and the second surface protrudes toward the mask so that a gap of 1 mm or less is opened from the mask. A screen printing apparatus formed. The mask holding means is configured such that a tangent of a tip portion of the first surface at a boundary portion where the first surface and the second surface are in contact is lower than horizontal with respect to a moving direction during printing of the squeegee. 2. The screen printing apparatus according to claim 1, wherein the screen printing apparatus is in a range of 5 to 80 degrees with respect to the surface of the mask held in the mask . The concave portion of the squeegee is formed so that the solder paste rolls inside the concave portion when driven by the squeegee driving means while the squeegee is pressed against the mask during the printing. The screen printing apparatus according to claim 1, wherein the screen printing apparatus is a screen printing apparatus. When the squeegee is pressed against the mask, the solder paste is placed between the mask and the tip of the concave first surface, which is a boundary between the first surface and the second surface . The screen printing apparatus according to claim 3, wherein a gap that is ten times the average particle diameter of the particles is formed. The screen printing apparatus according to claim 4, wherein the squeegee is formed of a resin whose main component is urethane and has a hardness of 80 degrees or more. A screen printing method using the screen printing apparatus according to claim 1 . The screen printing method according to claim 6, wherein a mask formed of a metal plate is used as the mask. The screen printing method according to claim 6, wherein a mask formed of a metal mesh is used as the mask.

Images