Improved stencil separation for printing

Abstract

To provide controlled separation between the printing screen and the workpiece. [Solution] The separation of the printing screen or stencil following the printing operation from at least one detached workpiece is controlled by the selective vertical movement of a surround plate. In particular, an upward force may be applied to the surround plate after printing, before separation, and / or during separation. A drive means is provided to control the movement of the surround plate, which is conveniently located between the surround plate and the transport unit.

Description

Technical Field

[0001] The present invention relates to a printing machine for printing a printing medium on a singulated workpiece held within a carrier, and a method for printing a printing medium on a singulated workpiece.

Background Art

[0002] Industrial screen printing machines typically apply a conductive printing medium, such as solder paste or conductive ink, onto a flat workpiece, such as a circuit board, by applying the conductive printing medium through a pattern of openings in a printing screen (sometimes referred to as a foil or stencil) using an angled blade or squeegee held by a print head. When the area of the pattern is relatively small compared to the area of the screen, it is possible to include multiple patterns within the screen, thereby enabling multiple substrates to be printed simultaneously using the same screen.

[0003] This can be achieved by pre-separating, i.e., "singulating", individual substrates prior to the printing process. Here, defective substrates are identified prior to printing and immediately discarded, so that only non-defective substrates are printed. This process is relatively efficient but introduces complexity. In particular, it is difficult to support and align individual relatively small substrates for simultaneous (or sequential) printing.

[0004] Various approaches have been developed to overcome these problems. For example, British Patent GB 2484373A describes a method in which individual substrates are positioned individually, but this only allows for sequential printing of one substrate at a time. Japanese Patent Publication 2009-248551 describes a method in which the position of each substrate is checked individually, and each substrate is sequentially repositioned using a repositioning arm. This technique allows all substrates on a panel to be printed simultaneously, but it requires additional equipment (i.e., a positioning arm), and moving the arm between workpieces is time-consuming. International Publication WO2014 / 166956 describes an alternative apparatus in which all substrates can be supported on their respective "towers," simultaneously aligned using a reference webbing, and then printed simultaneously. This solution works well, but it is not suitable when the incoming unprinted substrate is considerably far from the correct position.

[0005] A workpiece support assembly capable of supporting and individually aligning a number of relatively small workpieces (commonly referred to as “fragmented” workpieces) is described in European Patent No. EP3693168A1. Figure 2 schematically shows an example of such an assembly 4, which includes a 2x4 array of individual support “towers” ​​5. Each tower 5 carries a support surface 6 on which a workpiece (not shown) can be supported during printing. Furthermore, each tower 5 is individually actuated to move in orthogonal directions X and Y, which would typically lie in the horizontal plane, and is also actuated to rotate around an orthogonal Z axis, which would typically extend vertically to provide so-called θ correction. As described in European Patent No. EP3693168A1, such movement can be advantageously provided through the use of a parallel kinematic actuation system within each tower. Other arrays of larger or smaller dimensions are, of course, also possible. This system has been released by ASMPT under the name “MASS,” which provides a very fast and accurate printing solution.

[0006] If, during printing, the individualized workpieces are supported by a tower, the individualized workpieces are transported into the printing press by a carrier, which is a tray having an open-base receptacle on which each individualized workpiece rests, with contact on the underside of each workpiece, and which can be passed over as the tower passes over it.

[0007] Figure 1 is a fairly schematic side view showing such a known system immediately after the carrier 12 has been transported into the printing press. In this example, the carrier 12 can hold eight individualized workpieces W in a 2x4 array. In Figure 1, only four of these individualized workpieces W can be seen. The carrier 12 is transported by a conveyor unit 5, which comprises two conveyor belts (sometimes referred to as "rails") on which two sides of the carrier 12 rest. In Figure 1, the conveyor belts themselves are not shown for clarity, but it can be understood that they may actually be mounted on inwardly projecting "protrusions" on which the carrier 12 is supported. The conveyor unit 5 is supported by a hard stop 6, which is rigidly fixed to the printing press. The conveyor unit 5 may be displaced upward away from the hard stop 6, as will be described in more detail below. The conveyor unit 5 also supports a surround plate 7, which comprises a flat plate with a number of openings 8 formed therein, each opening 8 being sized to receive a detached workpiece W when in use. The surround plate 7 is positioned below the printing screen 9 and is patterned with openings corresponding to the required positions for the deposition of printing medium on the detached workpiece W, as described above. When in use, the printing medium is spread through the openings by moving the print head 10 together with the squeegee 11 across the upper surface of the printing screen 9.

[0008] To initiate the printing operation, the conveyor unit 5 transports the carrier 12 until it is positioned on the tooling. In this case, the tooling includes a plurality of tooling towers 2, one for each workpiece W, which extend upward from the tooling base 14 and may provide electrical and / or pneumatic connections to each tower. The tooling base 14 is then supported on the tooling table 1. Support surfaces 3 are provided at the upper end of each tower 2, each supporting a workpiece W when in use, which will be described in more detail below. The tooling table 1 is driveable vertically, i.e., parallel to the vertical axis or the "Z" axis, by table driving means (not shown). Vertical movement of the tooling table 1 naturally causes corresponding vertical movement of each of the towers 2. Also schematically illustrated as being associated with the tooling table 1 are contact members 4, which are arranged and configured to contact the conveyor unit 5 as described below.

[0009] Next, as shown in Figure 2, the tooling table 1 is lifted upward. The tower 2 passes through the open receptacle of the carrier 12, lifting each individualized workpiece W away from the carrier 12 and placing it into the opening 8 of the surround plate 7, with the top of the surround plate 7 at or slightly below the top of the workpiece W. At this height, the contact member 4 moves and makes contact with the conveyor unit 4.

[0010] Next, as shown in Figure 3, the tooling table 1 continues to move upward. The tower 2 continues to move the workpiece W upward, and due to the reaction of the contact member 4 with the conveyor unit 5, the conveyor unit 5 and the surround plate 7 are also lifted upward at the same speed as the workpiece W. This lift is continued until the workpiece W reaches the printing height and is pressed against the underside of the printing screen 9, as well as the surround plate 7. Together, the surround plate 7 and the workpiece W give the squeegee 11 a substantially flat surface as it passes over the printing screen 9, avoiding the squeegee "bouncing". The printing medium 13 introduced onto the upper surface of the printing screen 9 is spread within the opening of the printing screen 9 and thus spread onto the upper surface of the fragmented workpiece W.

[0011] Following printing, as schematically shown in Figure 4, the tooling table 1 is lowered, which then causes the tower 2, conveyor unit 5, and surround plate 7 to descend simultaneously, separating the printed workpiece W from the printing screen 9. As the tooling table 1 continues to descend, the printed workpiece W is returned to the carrier 12. After the tower 2 moves away from the carrier 12, the carrier 12 may be transported away from the printing press and replaced with a new carrier (not shown) holding an unprinted workpiece inside. This sequence may then be repeated throughout the current printing operation.

[0012] As is evident from the relatively small mass of the fragmented workpiece W, the separation of the workpiece from the printing screen 9 may be relatively jerky or even violent, and this separation adversely affects the print deposit on the workpiece W. During separation, the central portion of the printing screen 9 changes from resting on a relatively large area, i.e., an area of ​​the total surface area of ​​the surround plate 7 which may be relatively large compared to the size of the fragmented workpiece W, to being completely unsupported. This can then cause "wobbling" within the printing screen 9, which means fluctuations in the tension acting on the printing screen 9, and this, combined with fluctuations in the coplanarity from the screen to the workpiece, can adversely affect the print deposit during separation. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] British Patent No. GB ​​2484373 A [Patent Document 2] Japanese Patent Publication No. 2009-248551 [Patent Document 3] International Publication No. WO2014 / 166956 [Patent Document 4] European Patent No. EP3693168A1 [Overview of the project] [Problems that the invention aims to solve]

[0014] This invention aims to solve this problem. In particular, this invention aims to provide controlled separation between the printing screen and the workpiece.

[0015] According to the present invention, this objective is achieved by controlling the separation using a surround plate. In particular, an upward force may be applied to the surround plate after printing, before separation, and / or during separation. [Means for solving the problem]

[0016] According to a first aspect of the present invention, a printing machine is provided for printing a printing medium on individualized workpieces held in a carrier, which A tooling that is vertically movable within a printing press, and includes a support surface for supporting a sectional workpiece thereon, A transport means for positioning the carrier above the tooling such that the individualized workpieces held within the carrier are positioned above the support surface, A surround plate having an opening sized to receive a workpiece that has been separated into individual pieces during use, and comprising a surround plate positioned above the tooling and carrier during use, The printing press includes a drive mechanism mechanically engaged with a surround plate, the drive mechanism being capable of driving the surround plate vertically upward relative to the tooling.

[0017] A second aspect of the present invention provides a method for printing a printing medium onto a fragmented workpiece, which i) The step of placing the individualized workpieces into the carrier, ii) A step of transporting the carrier into the printing press, wherein the printing press A tooling that is vertically movable within a printing press, and includes a support surface for supporting a sectional workpiece thereon, A step comprising a surround plate having an opening sized to receive a workpiece that has been separated into individual pieces during use, and positioned above the tooling, iii) A step of positioning the carrier above the tooling so that the individualized workpieces are positioned above the support surface, iv) The step of lifting the tooling so that the support surface contacts the fragmented workpiece, lifting it from the carrier and placing it into the opening of the surround plate, v) depositing a printing medium onto the individualized workpieces by spreading the printing medium over an upper surface of a printing screen disposed above the individualized workpieces; vi) separating the individualized workpieces from the printing screen by lowering the tooling, where step vi) includes raising a surround plate relative to the tooling.

[0018] Other specific aspects and features of the invention are set forth in the appended claims.

[0019] Next, the invention will be described with reference to the accompanying drawings (not to scale).

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic view seen from the side showing steps in a known printing process using a standard printing apparatus. [Figure 2] It is a schematic view seen from the side showing steps in a known printing process using a standard printing apparatus. [Figure 3] It is a schematic view seen from the side showing steps in a known printing process using a standard printing apparatus. [Figure 4] It is a schematic view seen from the side showing steps in a known printing process using a standard printing apparatus. [Figure 5] It is a schematic view seen from the side showing steps in a printing process according to an embodiment of the invention. [Figure 6] It is a schematic view seen from the side showing steps in a printing process according to an embodiment of the invention. [Figure 7] It is a schematic view seen from the side showing steps in a printing process according to an embodiment of the invention. [Figure 8] It is a schematic view seen from the side showing steps in a printing process according to an embodiment of the invention. [Figure 9] This is a schematic diagram, viewed from the side, showing the steps in the printing process according to an embodiment of the present invention. [Figure 10] This is a schematic diagram, viewed from above, showing a surround plate and driving means according to an embodiment of the present invention. [Modes for carrying out the invention]

[0021] One embodiment of the present invention is shown in Figures 5 to 9. This apparatus shares many similarities with the apparatus in Figures 1 to 4, and therefore the reference numbers are retained as much as possible.

[0022] Figure 5 is similar to Figure 1 and is a highly schematic side view showing the system immediately after the carrier 12 has been transported into the printing press. In this example, the carrier 12 can hold eight individualized workpieces W in a 2x4 array. In Figure 5, only four of these individualized workpieces W can be seen. The carrier 12 is transported by a transport means including a conveyor unit 5, which comprises two conveyor belts (sometimes referred to as "rails") on which two sides of the carrier 12 rest. In Figure 5, the conveyor belts themselves are not shown for clarity, but it can be understood that they may actually be mounted on inwardly projecting "protrusions" on which the carrier 12 is supported. The conveyor unit 5 is supported by hard stops 6, which are rigidly fixed to the printing press. The conveyor unit 5 may be displaced upward away from the hard stops 6, as will be described in more detail below. The conveyor unit 5 also supports a surround plate 7, which comprises a flat plate having a number of openings 8 formed therein, each opening 8 having dimensions such that it can receive a detached workpiece W when in use. According to this embodiment, the printing press comprises a drive means 15 mechanically engaged with the surround plate 7, in which case the surround plate 7 is supported by the conveyor unit 5 via the drive means 15. The drive means 15 includes at least one linear actuator capable of operating to drive the surround plate 7 perpendicular to both the conveyor unit 5 and the tooling (i.e., the tower 2 and tooling base 14 described below), i.e., parallel to the vertical axis or the "Z" axis.

[0023] The surround plate 7 is positioned below the printing screen 9 and is patterned with openings corresponding to the required positions for the deposition of the printing medium on the sectional workpiece W, as described above. During use, the printing medium is spread through the openings by moving the print head 10 together with the squeegee 11 across the upper surface of the printing screen 9.

[0024] To initiate the printing operation, the conveyor unit 5 transports the carrier 12 until it is positioned on the tooling. In this case, the tooling includes a plurality of tooling towers 2, one for each workpiece W, which extend upward from the tooling base 14 and may provide electrical and / or pneumatic connections to each tower. The tooling base 14 is then supported on the tooling table 1. Support surfaces 3 are provided at the upper ends of each tower 2, each supporting a workpiece W when in use, which will be described in more detail below. The tooling table 1 is driveable vertically, i.e., parallel to the vertical axis or the "Z" axis, by table driving means (not shown). Vertical movement of the tooling table 1 naturally causes corresponding vertical movement of each of the towers 2. Also schematically illustrated as being associated with the tooling table 1 are contact members 4, which are arranged and configured to contact the conveyor unit 5 as described below.

[0025] Next, as shown in Figure 6, the tooling table 1 is lifted upward. The tower 2 passes through the open receptacle of the carrier 12, lifting each individualized workpiece W away from the carrier 12 and placing it into the opening 8 of the surround plate 7, with the top of the surround plate 7 at or slightly below the top of the workpiece W. At this height, the contact member 4 moves and makes contact with the conveyor unit 4.

[0026] Next, as shown in Figure 7, the tooling table 1 continues to move upward. The tower 2 continues to move the workpiece W upward, and due to the reaction of the contact member 4 with the conveyor unit 5, the conveyor unit 5 and the surround plate 7 are also lifted upward at the same speed as the workpiece W. This lift is continued until the workpiece W reaches the printing height and is pressed against the underside of the printing screen 9, as well as the surround plate 7. Together, the surround plate 7 and the workpiece W give the squeegee 11 a substantially flat surface as it passes over the printing screen 9, avoiding the squeegee "bouncing". The printing medium 13 introduced onto the upper surface of the printing screen 9 is spread within the opening of the printing screen 9 and thus spread onto the upper surface of the fragmented workpiece W.

[0027] Following printing, the drive mechanism 15 is operated to raise the surround plate 7 relative to the conveyor unit 5, as schematically shown in Figure 8. Then, and / or simultaneously, the tooling table 1 is lowered, as shown in Figures 8 and 9, to further separate the printed workpiece W from the printing screen 9, lowering the conveyor unit 5 and returning the workpiece W to the carrier 12. The relative timing of the operation of the drive mechanism 15 and the lowering of the tooling table 1 is flexible, and various examples are described in more detail below.

[0028] The drive mechanism 15 is activated to return the surround plate 7 to its initial position relative to the conveyor unit 5, and after the tower 2 has moved away from the carrier 12, the carrier 12 with the printed workpieces W is carried out of the printing press and removed, and replaced with a new carrier (not shown) with the unprinted workpieces held therein. This sequence may then be repeated throughout the current printing operation.

[0029] As mentioned above, the relative timing between the operation of the drive mechanism 15 and the descent of the tooling table 1 from the printing position shown in Figure 7 is flexible. An example schedule is as follows: 1) The surround plate 7 is raised before the tooling table 1 begins to descend. In this way, the surround plate 7 is pushed up into the printing screen 9 before the tower 2 is lowered. This approach ensures controllable tension within the printing screen 9, minimizes "wobbling" of the printing screen 9 during separation, and is also easy to control. 2) Raise the surround plate 7 relative to the conveyor unit 5, as if the tooling table 1 (and therefore the conveyor unit 5) were being lowered. This approach can help minimize the stress on the printing screen 9. In a particularly preferred embodiment, the surround plate 7 is driven upward by the drive means 15 at the same speed as the tooling table 1 is lowering, so that the surround plate 7 is kept at a substantially constant absolute height for at least part of the step of lowering the tooling table 1. This approach minimizes the stress generated in the printing screen 9 and is somewhat faster than the approach described in 1) above. 3) Either before or during the lowering of the tooling table 1, the first portion of the surround plate 7 is raised relative to the second portion of the surround plate 7. In this way, the surround plate 7 can be rotated and separated from a purely horizontal direction. This technique may be used to achieve a smooth "peel" of the print screen 9 from the printed workpiece W, or to control the tension within the print screen 9 at its precise location. In one example of this schedule, different portions of the surround plate 7 may be raised in accordance with the spreading direction of the squeegee 11 across the upper surface of the print screen 9. Typically, in a continuous printing operation, the print head moves in alternating directions, i.e., in the forward and backward directions of two opposing, aligned horizontal directions across the print screen 9. Therefore, it may be beneficial to adjust the inclination of the surround plate 7 with respect to this spreading direction.

[0030] Regarding schedule 3) above, such tilt control of the surround plate 7 can be achieved using a device such as the one schematically shown from above in Figure 10, where a 4x2 array of openings 8 within the surround plate is shown in the figure. The surround plate 7 is shown transparent so that three actuators 15A, 15B, and 15C, together forming a drive means 15, are visible. Each of these actuators 15A, 15B, and 15C engages with the surround plate 7 at a position horizontally spaced apart around the surround plate 7. Using three actuators 15A, 15B, and 15C spaced apart in each horizontal axis is the minimum work required to control the pitch and roll of the surround plate 7. However, arrangement configurations including at least one additional actuator can also be used equally.

[0031] The embodiments described above are illustrative only, and other possible means and alternatives within the scope of the present invention will be apparent to those skilled in the art. [Explanation of Symbols]

[0032] 1 Touring Table 2 Touring Tower 3 Support surface 4 Contact Member 5 Conveyor Units 6. Hard Stop 7 Surround Plate 8 openings 9 Print Screen 10 printheads 11 squeegee 12 carriers 13 Print media 14 Touring Base 15 Driving means 15A, 15B, 15C actuators W Workpiece

Claims

1. A printing press for printing a printing medium onto individual workpieces held within a carrier, A tooling that is vertically movable within the printing press, and includes a support surface for supporting the individualized workpiece thereon, A transport means for positioning the carrier above the tooling such that the individualized workpieces held within the carrier are positioned above the support surface, A surround plate having an opening sized to receive the individualized workpiece during use, the surround plate being positioned above the tooling and the carrier during use, Equipped with, The printing press comprises a drive means mechanically engaged with the surround plate, the drive means capable of driving the surround plate vertically upward relative to the tooling.

2. The printing press according to claim 1, comprising a vertically movable lifting table, wherein the tooling is supported on the lifting table so as to move vertically with it.

3. The printing press according to claim 1, wherein the surround plate is supported by the transport means via the drive means, and thereby the surround plate is movable relative to the transport means in a direction perpendicular to the transport means.

4. The printing press according to claim 1, wherein the driving means includes at least three vertical actuators that engage with the surround plate, each at a horizontally separated position around the surround plate.

5. The printing press according to claim 4, wherein the at least three vertical actuators are independently drivable.

6. A method for printing a printable medium onto individual workpieces, i) The step of placing the individualized workpiece into the carrier, ii) A step of transporting the carrier into the printing press, wherein the printing press is A tooling that is vertically movable within the printing press, and includes a support surface for supporting the individualized workpiece thereon, A step comprising: a surround plate having an opening sized to receive the sectional workpiece during use, and positioned above the tooling; iii) The step of positioning the carrier above the tooling such that the individualized workpieces are positioned above the support surface, iv) The steps of lifting the tooling so that the support surface contacts the individualized workpiece, lifting it from the carrier and placing it into the opening of the surround plate, v) The step of depositing the printing medium onto the fragmented workpiece by spreading the printing medium onto the upper surface of a printing screen located above the fragmented workpiece, vi) The step of separating the fragmented workpiece from the printing screen by lowering the tooling, Includes, Step vi) a method comprising raising the surround plate relative to the tooling.

7. The method according to claim 6, wherein step vi) includes raising the surround plate relative to the print screen, thereby pushing it into the print screen, before lowering the tooling.

8. The method according to claim 6, wherein step vi) includes raising the surround plate relative to the tooling when the tooling is lowered.

9. The method according to claim 8, wherein step vi) includes raising the surround plate relative to the tooling so that it remains at a constant height for at least a portion of the step.

10. The method according to claim 6, wherein step vi) includes raising the first portion of the surround plate relative to the second portion of the surround plate.

11. The method according to claim 10, wherein step v) includes moving the squeegee across the upper surface of the printing screen in a spreading direction including one of two opposing and aligned horizontal directions, the first portion of the surround plate being selected according to the spreading direction.

12. The method according to claim 6, wherein step i) includes the step of placing a plurality of individualized workpieces into the carrier.

13. The method according to claim 12, wherein step v) includes the step of depositing the printing medium onto the plurality of fragmented workpieces by spreading the printing medium across the upper surface of the printing screen in a single spreading motion.

14. Step v) includes the step of depositing a printing medium onto a single workpiece from among the plurality of individualized workpieces, and the method is vii) Moving the carrier so that different individual workpieces among the plurality of individual workpieces are positioned above the support surface, and then viii) Repeating steps iv) to vii) until each of the workpieces has a printing medium deposited on it, The method according to claim 12, further comprising:

15. The method according to claim 6, wherein the printing press includes the printing press described in claim 1.

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