Technical Field

The present disclosure generally relates to a scraper assembly in a stencil printer for printing a viscous material, such as a solder paste, onto a substrate, such as a printed circuit board.

Background Art

In typical circuit board production processes, a stencil printer is used to print a solder paste onto a printed circuit board. The circuit board, which is also referred to broadly as an electronic substrate, has a pattern of solder pads or some other conductive surfaces that may deposit a solder paste, and the circuit board is automatically fed into a stencil printer. Certain holes or markings on the circuit board, referred to as reference points, are used to align the circuit board with a stencil or mesh board of a stencil printer before printing the solder paste onto the circuit board. The reference points are used as points for reference when aligning the circuit board with the stencil. Once the circuit board is aligned with the stencil of the printer, the circuit board is raised to the stencil by a substrate support and fixed relative to the stencil, and the stencil support may be, for example, a platform having a pm or other item support. The solder paste is then dispensed by moving a scraper or squeegee over the stencil so that the solder paste passes through the holes in the stencil and onto the circuit board. The solder paste is typically dispensed on the stencil from a standard solder paste feed cartridge. Upon completion of the printing operation, the circuit board is released, lowered, and detemplated before being conveyed to another location within a printed circuit board production line.

As the squeegee moves through the stencil, the solder paste rolls in front of the scraper, which causes the solder paste to be mixed as desired to obtain a desired viscosity to help fill the holes in the mesh board or stencil. A pair of baffles are placed on opposite sides of the scraper, which may retain the solder paste on the travel path of the scraper for better mixing and dispensing of the solder paste. Summary of the Invention

According to a first aspect of the present disclosure, the present disclosure provides a squeegee assembly for a stencil printer, including: a scraper mount; a scraper, which has a travel path for scraping a material to be dispensed; a scraper holder, which includes a connecting portion and a support portion connected to each other, the support portion being positioned under the connecting portion and supporting the scraper, the scraper holder being connected to the scraper mount through a top surface of the connecting portion, wherein the connecting portion has a pair of first ends located on opposite sides of the travel path of the scraper, the support portion has a pair of second ends located on opposite sides of the travel path of the scraper, and the pair of second ends are respectively retracted relative to the pair of first ends to form a pair of mounting spaces under the connecting portion; a pair of baffles held at the pair of second ends of the support portion to position the pair of baffles on opposite sides of the travel path of the scraper, wherein the pair of baffles are movable up and down relative to the support portion, and wherein the pair of baffles are each positioned at least partially in the pair of mounting spaces; a pair of mounting blocks connected to the connecting portion of the scraper holder, the pair of baffles being positioned respectively between the pair of second ends of the support portion and the pair of mounting blocks; and a pair of elastic pieces respectively connected to the pair of mounting blocks and extending to a position above the pair of baffles respectively, the pair of elastic pieces being configured to be urged by the baffles to deform elastically as the pair of baffles move upward, and enable the pair of baffles to move downward through a restoring force.

According to the squeegee assembly described above, the pair of baffles are respectively connected to the pair of mounting blocks while being movable up and down.

According to the squeegee assembly described above, a top surface of the baffle includes an acting surface for interacting with the elastic piece, the acting surface positioned outside the mounting space, wherein the elastic piece extends to a position above the acting surface. According to the squeegee assembly described above, the top surface of the baffle further includes a concession surface that is lower than the acting surface, the concession surface being located in the mounting space.

According to the squeegee assembly described above, at least one guide slot extending in an up-and-down direction is provided on the baffle, the squeegee assembly further includes at least one fastener matched with the at least one guide slot to connect the baffle to the pair of mounting blocks while allowing the baffle to move up and down.

According to the squeegee assembly described above, the mounting block includes a first portion and a second portion connected to each other, the first portion being located in the mounting space, the second portion being located outside the mounting space, wherein the elastic piece is connected on a top surface of the second portion.

According to the squeegee assembly described above, when the baffle is located in its lowest position, the acting surface of the baffle is generally located on an extending surface of the top surface of the second portion of the mounting block.

According to the squeegee assembly described above, the pair of baffles are configured to retain a material to be dispensed on the travel path of the scraper.

According to the squeegee assembly described above, the scraper has a length perpendicular to its travel path, and a distance between the pair of baffles is slightly greater than the length of the scraper.

According to a second aspect of the present disclosure, the present disclosure provides a stencil printer including the squeegee assembly according to the first aspect described above.

Brief Description of Drawings

Fig. 1 is a stereoscopic view of a stencil printer according to one example of the present disclosure;

Fig. 2A is a stereoscopic view of one perspective of a squeegee assembly according to one example of the present disclosure; Fig. 2B is a stereoscopic view of another perspective of the squeegee assembly of Fig.

2A;

Fig. 2C is a partially exploded view of the squeegee assembly shown in Fig. 2A;

Fig. 3A is an assembly view of one perspective of a scraper holder and a scraper in the squeegee assembly shown in Fig. 2A;

Fig. 3B is an assembly view of another perspective of the scraper holder and the scraper in the squeegee assembly shown in Fig. 2A;

Fig. 3C is an exploded view of one perspective of the scraper holder and the scraper in the squeegee assembly shown in Fig. 2A;

Fig. 3D is an exploded view of another perspective of the scraper holder and the scraper in the squeegee assembly shown in Fig. 2A;

Fig. 4 is a stereoscopic view of a baffle in the squeegee assembly shown in Fig. 2A;

Fig. 5 is a stereoscopic view of the assembled baffle and mounting block in the squeegee assembly shown in Fig. 2A.

Description of Embodiments

Various specific embodiments of the present disclosure will be described below with reference to the appended drawings that form a part of the present specification. It should be understood that while terms denoting orientation, such as “front”, “rear”, “upper”, “lower”, “left”, “right”, “top”, “bottom”, etc., are used in the present disclosure to describe various exemplary structural parts and elements of the present disclosure, these terms are used herein for convenience of illustration only and are determined based on the exemplary orientations shown in the appended drawings. Since the examples disclosed in the present disclosure may be disposed in different orientations, these terms denoting orientation are for illustrative purposes only and should not be considered as limiting. Fig. 1 is a stereoscopic view of a stencil printer 100 according to one example of the present disclosure. As shown in Fig. 1, the stencil printer 100 includes a rack 110 that supports various components of the stencil printer. The components of the stencil printer 100 include a controller 120, a display 125, a stencil 130, and a print head assembly or print head 140 for applying a solder paste. The stencil 130 and the print head 140 may be suitably coupled or connected to the rack 110. In an example, the print head 140 may be mounted on a print head bracket 150, and the print head bracket 150 may be mounted on the rack 110. Under the control of the controller 140, the bracket 150 is capable of moving the print head 140 in a Y-axis direction perpendicular to an X-axis and a Z-axis. The print head 140 may be placed above the stencil 130 and a front scraper or a rear scraper of the print head 140 may be lowered in the Z-axis direction into contact with the stencil 130. Through the bracket 150, the scraper of the print head 140 may then move passing through the stencil 130 such that the solder paste is printed onto a circuit board.

The stencil printer 100 may also include a conveying system including a track 160 that is used to transport a printed circuit board (sometimes referred to as a “printing circuit board,” “substrate,” or “electronic substrate”) to a printing location inside the stencil printer 100. The track 1 0 is also referred to herein as a “feed-in mechanism” configured to provide, load, or transport a circuit board to a working area of the stencil printer 100 and remove the circuit board from the working area. The stencil printer 100 has a support assembly 170 to support a circuit board

In some examples, the print head 140 may be disposed to obtain solder material from a source such as a dispenser (for example, a solder paste cartridge) that provides the solder paste to the print head dunng a printing operation. Other methods of providing a solder paste may also be used in place of the solder paste cartridge. For example, the solder paste may be deposited manually between scrapers or the solder paste may also be from an external source. Further, in some examples, the controller 120 may be set up to control operation of the stencil printer 100 using a personal computer with a Microsoft DOS or Windows XP operating system having application-specific software. The controller 120 may be networked with a host controller that is used to control a production line of manufacturing circuit boards.

In some examples, the stencil printer 100 operates as follows. The circuit board is fed into the stencil printer 100 in the X-axis direction through the conveying track 160. The support assembly 170 raises and secures the circuit board in the printing position. The print head 140 then lowers a desired print head scraper in the Z-axis direction until the print head scraper contacts the stencil 130 at a desired pressure. The print head 140 is then moved through the stencil 130 in the Y-axis direction by the print head bracket 150. The print head 140 deposits the solder paste through the holes in the stencil 130 to fall on the circuit board. Once the print head 140 is fully across the stencil 130, the scraper is lifted away from the stencil 130 and the circuit board is lowered back to the conveying track 160. Subsequently, the circuit board is released and output from the stencil printer 100 so that a second circuit board can be loaded into the stencil printer 100. In order to print on the second circuit board, another scraper is brought into contact with the stencil along the Z-axis and the print head 140 is moved passing the stencil 130 in a direction opposite to that used for the first circuit board.

Still referring to Fig. 1, an imaging system 180 may be provided for aligning the stencil 130 with the circuit board before printing and inspecting the circuit board after printing. In an example, the imaging system 180 may be disposed between the stencil 130 and the support assembly 170 supporting the circuit board. The imaging system 180 is connected to an imaging bracket 185 to move the imaging system. In an example, the imaging bracket 185 may be connected to the rack 110 and the imaging bracket 185 includes a beam extending between side rails of the rack 110 to allow the imaging system 180 to move back and forth in the Y-axis direction above the circuit board. The imaging bracket 185 may also include a transport device enclosing the imaging system 180 from outside and disposed to move in the X-axis direction along a length direction of the beam. The structure of the imaging bracket 185 for moving the imaging system 180 is well known in the field of solder paste printing. The approach is as follows. The imaging system 180 may be located at any location under the stencil 130, above the circuit board, in order to obtain an image of a predetermined area of the circuit board or the stencil, respectively.

In an example, the print head 140 includes a frame member 145 that forms a portion of the bracket 150. The frame member 145 is configured to move along a printing direction, such as the Y-axis direction. In particular, the frame member 145 is configured to slide along a linear track (not shown in Fig. 1) of the rack 110 of the stencil printer 100 at opposite ends thereof. This structure allows the print head bracket 150 to move in the Y-axis direction. In an example, the frame member 145 supports a squeegee assembly having a front scraper and a rear scraper and a movement mechanism configured to move the scrapers independently. Under the control of respective movement mechanisms, each scraper is configured to move along the Z-axis direction from a higher position having a certain spacing with the stencil to a lower position engaging the stencil and applying pressure to the stencil.

Figs. 2A to 2C illustrate an overall structure of a squeegee assembly 200 according to one example of the present disclosure, wherein Fig. 2A is a stereoscopic view of one perspective of the squeegee assembly 200, Fig. 2B is a stereoscopic view of another perspective of the squeegee assembly 200 in Fig. 2A, and Fig. 2C is a partially exploded view of the squeegee assembly 200 shown in Fig. 2A. As shown in Figs. 2A to 2C, the squeegee assembly 200 includes a scraper 220 and a scraper mount 210 and a scraper holder 220 for mounting the scraper 220. The scraper 220 is, for example, a front scraper, and for ease of illustration, only the front scraper and mounting components thereof are shown in the squeegee assembly 200 shown in Figs. 2A to 2C, while the rear scraper and mounting components thereof are removed. The scraper 220 has a travel path for scraping a material (solder paste) to be dispensed, and the travel path extends along the Y-axis direction. The scraper holder 230 is used to support the scraper 220, and the scraper mount 210 is used to connect the scraper holder 230 to a movement mechanism (not shown in the drawing) of the scraper.

The squeegee assembly 200 also includes a pair of baffles 250 and a pair of mounting blocks 260 that hold the pair of baffles 250 on opposite sides of the travel path of the scraper 220, respectively. The pair of baffles 250 are used to retain the solder paste on the travel path of the scraper 220 so that the scraper 220 can scrape the solder paste, and as a result, the solder paste can pass through the holes in the stencil 130 onto the circuit board under the stencil 130. The pair of mounting blocks 260 are connected to the scraper holder 230 and the pair of baffles 250 are respectively connected to the pair of mounting blocks 260 to be movable up and down (along the Z-axis), so that the pair of baffles 250 are capable of moving up and down relative to the scraper holder 230 and the scraper 220 held on the scraper holder 230.

The scraper 220 needs to apply a certain amount of pressure on the stencil when scraping the solder paste, and thus the scraper mount 210 is lowered relative to the stencil 130 causing the scraper 220 to deform in order to apply the pressure. To retain the solder paste on the travel path of the scraper 220, it is necessary that the bottom most ends of the pair of baffles 250 and the bottom most end of the scraper 220 are all in contact with the stencil 130 when in operation. Thus, in order to retaining the solder paste on the travel path of the scraper 220 without affecting the operation of the scraper 220, the baffle 250 needs to be capable of moving up and down relative to the mounting block 230. That is, the baffle 250 needs to be moved upward when the scraper 220 applies a pressure to the stencil to deform, and the baffle 250 needs to be moved downward when the scraper 220 no longer applies a pressure to the stencil to restore it. In this way, the bottom most end of the baffle 250 is always on the same plane as the bottom most end of the scraper (i.e., both in contact with the stencil 130) and the baffle 250 is always holding the solder paste on the travel path of the scraper 220 without affecting the operation of the scraper 220. To enable the baffle 250 to move up and down relative to the mounting block 260 with the deformation of the scraper 220, the squeegee assembly 200 also includes a pair of elastic pieces 270 that are respectively connected to the pair of mounting blocks 260 and extend to positions above the pair of baffles 250 respectively. Moreover, the pair of elastic pieces 270 are configured to be urged by the baffles 250 to be resiliently deformed as the pair of baffles 250 move upward, and to enable the pair of baffles 250 to move downwardly by the restoring force. As shown in Fig. 2C, the mounting block 260 is connected to the scraper holder 230 by a fastener 283, the elastic piece 270 is connected to the mounting block 260 by a fastener 282, and the baffle 250 is connected to the mounting block 260 by a fastener 285.

Figs. 3A to 3D show the specific structure of the scraper holder 230 and the mounting structure of the scraper 220 of the squeegee assembly 200 in Fig. 2A. Here, Fig. 3A is an assembly view of one perspective of the scraper holder 230 and the scraper 220, Fig. 3B is an assembly view of another perspective of the scraper holder 230 and the scraper 220, Fig. 3C is an exploded view of one perspective of the scraper holder 230 and the scraper 220, and Fig. 3D is an exploded view of another perspective of the scraper holder 230 and the scraper 220. As shown in Figs. 3 A to 3D, the scraper holder 230 includes a connecting portion 310 and a support portion 350 connected to each other, and the support portion 350 is positioned under the connecting portion 310 for supporting or retaining the scraper 220. The scraper holder 230 is connected to the scraper mount 210 by a top surface 312 of the connecting portion 310. The connecting portion 310 has a pair of first ends 313, 315 located on opposite sides of the travel path of the scraper 220 and the support portion 350 has a pair of second ends 353, 355 located on opposite sides of the travel path of the scraper 220. The pair of second ends 353, 355 of the support portion 350 are retracted inwardly relative to the pair of first ends 313, 315 of the connecting portion 310, respectively, to form a pair of mounting spaces 370 located under the connecting portion 310 for mounting the pair of baffles 250 and the pair of mounting blocks 260.

The support portion 350 of the scraper holder 230 includes a first portion 352 and a second portion 354 detachably connected together. The top of the first portion 352 is connected to the connecting portion 310, for example, the first portion is integrally formed with the connecting portion 310. The second portion 354 is detachably connected by a fastener 380 to a side of the first portion 352 facing the solder paste to be scraped. The scraper 220 is in the form of a sheet that is clamped between the first portion 352 and the second portion 354 of the support portion 350. The scraper 220 has a blade 322 and a scraping surface 325. The blade 322 protrudes from the bottom of the scraper holder 230, and the scraping surface 325 faces towards the second portion 354. However, a majority of the scraping surface 325 is exposed without being blocked by the second portion 354, so that a majority of the area of the scraping surface 325 can be in contact with the solder paste to be scraped. The scraper 220 is generally held tilted relative to the Z-axis direction in the scraper holder 230 and tilted rearward relative to an advancing direction. When the scraper 220 is in operation, the blade 322 applies pressure to the stencil from one side of the scraping surface 325 such that the blade 322 bends towards the first portion 352.

The length of the scraper 220 (i.e., dimensions perpendicular to the scraping path thereof) is generally equal to the distance between the pair of second ends 353, 355 of the support portion 350. As a result, when the scraper 220 is mounted in place in the support portion 350, both ends of the scraper are aligned with the second end 353, 355 of the support portion 350, respectively. The pair of baffles 250 are held at the pair of second ends 353, 355 of the support portion 350 by the pair of mounting blocks 260, respectively, with a distance between the pair of baffles 250 being slightly greater than the distance between the pair of second ends 353, 355 of the support portion 350. As such, the distance between the pair of baffles 250 is slightly greater than the length of the scraper 220. With this configuration, the pair of baffles 250 can be moved up and down as close as possible to the scraper to better retain the solder paste on the travel path of the scraper.

Figs. 4 and 5 show a specific structure of the baffle 250 and the mounting block 260, wherein Fig. 4 is a stereoscopic view of the baffle 250 in the squeegee assembly 200 shown in Fig. 2A and Fig. 5 is a stereoscopic view of the assembled baffle 250 and mounting block 260 in the squeegee assembly 200 shown in Fig. 2A.

As shown in Fig. 4, the baffle 250 is generally rectangular with a top surface 410 thereof generally stepped. In particular, the top surface 410 includes an acting surface 412 for interacting with the elastic piece 270 and a concession surface 414 that is lower than the acting surface 412. When the baffle 250 is mounted in place, the concession surface 414 is located in the mounting space 370 of the support portion 350 (i.e., under the connecting portion 310) and the acting surface 412 is located outside the mounting space of the support portion 350. In the up-and-down direction, the acting surface 412 is capable of being moved above the mounting space 370. A long bar-shaped guide slot 420 provided on the baffle 250 extends along the up-and-down direction to allow the baffle 250 to be connected to the mounting block 260 while being capable of moving up and down. In some examples, the number of guide slots 420 is two, and the guiding slots are located under the acting surface 412 and the concession surface 414, respectively. A bottom end 430 of the baffle 250 and the bottom most end of the scraper 220 are both in contact with the stencil 130 when in operation.

As shown in Fig. 5, the mounting block 260 includes a first portion 510 and a second portion 520 connected to each other. When the mounting block 260 is mounted in place, the first portion 510 is located in the mounting space 370 of the support portion 350 (i.e., under the connecting portion 310), while the second portion 520 is located outside the mounting space 370. A proximal end of the elastic piece 270 is connected on a top surface 523 of the second portion 520 and a distal end of the elastic piece 270 extends to a position above the acting surface 412 of the baffle 250.

The baffle 250 is connected to the mounting block 260 by the fastener 285. The number of the fastener 285 is the same as the number of the guide slot 420. Each mounting aperture 420 is matched with a fastener 285 that is capable of moving up and down in the guide slot 420. The baffle 250 includes a lowest position and a highest position. When the baffle 250 is located in the lowest position, the baffle 250 is located at the bottommost position of its movement trajectory, and the fastener 285 is located at the topmost end of the guide slot 420. When the baffle 250 is located in the highest position, the baffle 250 is located in the upmost position of its movement trajectory and the fastener 285 is located at the bottom most end of the guide slot 420.

When the baffle 250 is located in its lowest position, the acting surface 412 of the baffle 250 is generally located on an extended surface of the top surface 523 of the second portion 520 of the mounting block 260, and the elastic piece 270 is pressed on the acting surface 412 of the baffle 250 and exerts a certain amount of pressure on the acting surface 412. When the scraper 220 begins to press the stencil 130 to scrape the solder paste, the blade 322 of the scraper 220 is pressured to deform from one side of the scraping surface 325 and the baffle 250 moves upwardly away from its lowest position under the action of the stencil 130 as the scraper 220 deforms. In this process, the elastic piece 270 is elastically deformed by an upward thrust exerted by the baffle 250, thereby accumulating a restoring force. When the baffle 250 is no longer subjected to the force of the stencil 130, the baffle 250 moves downwardly back to its lowest position under the action of the restoring force of the elastic piece 270. As such, the bottom most end of the baffle 250 is always coplanar with the bottom most end of the scraper 220 and the baffle 250 retains the solder paste on the travel path of the scraper without affecting the operation of the scraper 220. In addition, the blade 322 of the scraper 220 may be deformed as the use time becomes longer. By setting the baffle 250 to be capable of moving up and dow n, the bottom most end of the baffle 250 is always able to remain coplanar with the bottom most end of the scraper 220, regardless of whether or not the blade 322 of the scraper 220 is deformed.

For the squeegee assembly 200, the size of the top surface of the scraper holder 230 (i.e., the top surface 312 of the connecting portion 310) is limited by the scraper mount 210, and the length of the top surface 312 is at least the same as the general length of the bottom surface of the scraper mount 210 to facilitate mounting between the scraper holder 230 and the scraper mount 210. In the squeegee assembly 200 of the present disclosure, a mounting space beneath the connecting portion 310 is formed by dividing the scraper holder 220 into two portions having different length sizes, namely, the connecting portion 310 and the support portion 350, and causing the two ends of the support portion 350 defining the length thereof to retract inwardly relative to the ends of the connecting portion 310 defining the length thereof. Moreover, the present application arranges the baffle 250 and the mounting portion of the mounting block 260 under the connecting portion 310 such that the pair of baffles 250 are located at two ends of the support portion 350, respectively. As such, the distance between the pair of baffles 250 will not be limited by the distance between the two ends of the connecting portion 310 of the scraper holder 220, but instead may be adjusted depending on the length of the scraper 220 to allow the scraper holder 230 to adapt to a scraper 220 with a smaller size. Accordingly, the scraper that can be used in the squeegee assembly 200 according to the present application may be smaller in size to meet the production needs of the progressively miniaturized circuit board dimensions.

It is to be noted that although it is shown in the examples of the drawings that the baffle 250 is mounted on the mounting block 260, in other examples, the baffle 250 may also be mounted on both ends of the support portion 350 of the scraper holder 230, and these are all within the protective scope of the present application.

Although the present disclosure has been described in connection with examples outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or foreseeable now or in the near future, may be apparent to those having at least ordinary skill in the art. In addition, the technical effects and/or technical problems described in the present specification are exemplary and not limiting; therefore, the disclosure in the present specification may be used to solve other technical problems and have other technical effects and/or may solve other technical problems. Therefore, examples of the present disclosure as set forth above are intended to be illustrative and not limiting. Various changes may be made without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to include all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.