JP3593595B2 - PRINT HEAD AND PRINTING METHOD USING THE PRINT HEAD - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printing head for transferring and applying a paste through an opening of a mask onto a substrate such as a printed circuit board, and a printing method using the printing head.
[Prior art]
Conventionally, there is a print head that transfers and applies solder paste through an opening in a mask with a squeegee etc. arranged in a closed space on an electronic circuit board on which electronic components such as semiconductor devices and resistors and capacitors are mounted on the board Printing presses are known.
[0002]
2. Description of the Related Art A printing machine having a print head of this type is provided with a press-contact adjusting mechanism between a squeegee main body and a container and urges a pressing force to the other squeegee side as described in, for example, Japanese Patent Application Laid-Open No. 5-286115. By absorbing the contact pressure acting on one squeegee side and maintaining the balance of the pressure contact force, an even load is applied to the mask to prevent the formation of a gap between the squeegee body and the mask. In addition, the biasing force of each shaft is made variable according to the moving direction of the squeegee main body, and the front squeegee has a stronger pressing force than the rear squeegee, and is moved in the opposite direction when moving forward. At times, the squeegee at the rear can be adjusted to increase the pressing force.
[0003]
[Problems to be solved by the invention]
However, the technique described in the above-mentioned publication does not mention the influence on the printing accuracy due to the parallelism of the lower ends of the squeegees before and after the moving direction. That is, in the conventional printing press, the edges of the lower end of the squeegee that come into contact with the mask in the moving direction are not completely parallel and have a certain degree of inclination due to the manufacturing accuracy of the squeegee holder, the degree of squeegee polishing, and the mounting accuracy. In this state, when the squeegee is brought into contact with the screen mask so that a uniform load is applied to the screen mask, the pressing force at the lower end of the squeegee becomes non-uniform in the longitudinal direction due to the inclination (error) formed by the front and rear lower ends. When the substrate is twisted right and left around the moving direction as the central axis, the non-uniformity is further increased. The unevenness in the longitudinal direction of the pressing force at the lower end of the squeegee appears as it is as the unevenness of the printing shape, particularly the height, and has a drawback that it contributes to poor printing.
Further, in the prior art, when the moving speed is increased, pitching vibration is generated between the front and rear squeegees due to friction and balance between the front squeegee and the mask, and printability is deteriorated.
[0004]
An object of the present invention is to eliminate the above-mentioned disadvantages caused by the conventional technique, to extend the life of the paste by always keeping the paste in a sealed state even during printing, and to uniformly press the squeegee bottom pressing force in the longitudinal direction. Accordingly, an object of the present invention is to provide a print head capable of performing stable printing and a printing method using the print head.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a print head according to the present invention includes a pair of squeegees disposed so as to face each other in a moving direction, seals are provided at both ends of the pair of squeegees, and the inside of the print head is formed by the squeegee and the seal. And a driving unit provided with a pitch mechanism for rotating the sealing unit in the front-rear direction with respect to the moving direction and a roll mechanism for rotating the sealing unit in a direction perpendicular to the moving direction, wherein the pitch mechanism includes the outer shell and A piston which is provided substantially opposite to the rotating plate and which applies a rotating force for rotating the rotating plate; and a stage which is provided on the outer shell and the longitudinal end of the rotating plate and which is on the front side in the moving direction. of that includes a plurality of stoppers for limiting the pitching direction of the displacement of the first aspect, in the print head configuration and the second to the sealing portion and the driver unit are fastened with screws In a third aspect, in each of the print heads having the above-described features, a mechanism for supplying a solvent into the closed section is provided, and in any one of the print heads, a temperature for adjusting a temperature of a space in the closed section is provided. A fourth feature is that an adjustment mechanism is provided.
[0006]
Further, according to the printing method of the present invention, the paste is supplied to a closed space formed by a pair of squeegees provided before and after in the moving direction, and a seal portion and a mask provided on both ends of the squeegee, The closed space is rotated in the moving direction so that the pressing force of the rear squeegee on the mask is higher than that of the squeegee, and the printing operation is performed while applying a rotating force so that the longitudinal directions of the front and rear squeegees are substantially parallel. It is characterized by the following.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a print head and a printing method using the print head according to an embodiment of the present invention will be described with reference to the drawings.
1 is a perspective view showing a schematic structure of a print head according to the present embodiment, FIG. 2 is a cross section of the print head, FIGS. 3 to 5 are diagrams for explaining the operation of the print head, and FIGS. FIG.
[0008]
First, the configuration of the print head according to the present embodiment will be described with reference to FIGS. 1, 2, and 6. FIG. The print head is roughly divided into a sealing portion 1 mounted on a substrate and sealing an internal space between the substrate and the substrate, and is disposed above the sealing portion 1, and has a function of moving the sealing portion 1 up and down and a moving direction. The drive unit 2 has a function of rotating in the front-rear direction and a function of rotating in the right-angle direction. The drive unit 2 has an opening 6 at a position corresponding to the conductor pattern 5 provided on the substrate 4. It is connected to a pressing force applying mechanism (not shown) for controlling the pressing force applied to the mask 3 provided.
[0009]
<Description of Sealing Unit 1>
As shown in FIG. 2, the sealing portion 1 has an inner shell 11 having a closed upper portion fixed to the inside of a jacket 14, and squeegee holders 9 and 10 opened in an eight-shape inside the inner shell 11. One end of a squeegee 7 or 8 having an elastic force that bends is attached to each of the squeegee holders 9 and 10. The squeegees 7 and 8 and the squeegee holders 9 and 10 have the same dimension in the direction perpendicular to the direction of movement of the squeegee (here, referred to as the longitudinal direction), and the other ends of the squeegees 7 and 8 are flush. I have.
[0010]
A fluid introduction hole 47 is provided on one end side of the jacket 14 of the closed portion 1 in the longitudinal direction, and a fluid discharge hole 48 (FIG. 1) is provided on the other end side. A fluid passage groove 46 is provided between the jacket 14 and the inner shell. The fluid passage groove 46 communicates with a fluid introduction hole 47 and a fluid discharge hole 48.
[0011]
Furthermore, side seals 12 and 13 (see also FIG. 1) are fixed inside both ends of the inner shell 11 in the longitudinal direction so as to cover both ends of the inner shell 11. The end portions of the side seals 12 and 13 (contact portions with the mask) are also squeegees 7 and 8 so that the space surrounded by the five surfaces of the side seals 12 and 13, the squeegees 7 and 8, and the mask 3 is a closed space. Is formed so as to be flush with the other end of the.
[0012]
As described above, the sealing unit 1 according to the present embodiment includes the squeegee holders 9 and 10 attached to the inner shell 11, the squeegees 7 and 8 attached to the lower ends of the squeegee holders 9 and 10, and both ends of the inner shell 11. A closed space is formed by the closed side seals 12 and 13 and the mask 3.
<Description of drive unit 2>
Next, as shown in FIG. 2, the drive unit 2 is provided with an outer shell 18 located above the inner shell 11 and an upper side of the outer shell 18 to correct a longitudinal inclination (rolling). A roll balance portion 15 provided with a roll mechanism, a rotating plate 19 provided inside the outer shell 18, and a rotating force acting on the rotating plate 19 in the moving direction of the squeegee (herein referred to as the width direction) to cause the rotating plate 19 to rotate in the pitch direction. It is composed of cylinder units 16 and 17 which are pitch mechanism units for performing correction.
[0013]
To the outer shell 18, as shown in FIG. 1, the stopper 34, 35, and 36 are provided to limit the displacement of the pitch Direction of the rotating plate 19. Although only three stoppers are visible in FIG. 1 of the present apparatus, stoppers are also provided at portions facing the stopper 35. With these configurations, the drive unit 2 according to the present embodiment is configured such that a pitch mechanism rotatable in the front-rear direction with respect to the traveling direction of the squeegee and a roll mechanism rotatable in a direction perpendicular to the squeegee can be provided to correct the sealing unit 1. It is.
[0014]
At both ends in the longitudinal direction of the rotary plate 19, insertion holes for fastening with the above-mentioned sealing portion 1 by screws are provided, and portions corresponding to the positions of the insertion holes of the jacket 14 constituting the sealing portion 1. Is provided with a screw hole 33, and the rotating plate 19 is supported by the outer shell 18 at a central portion in the longitudinal direction by a pitch shaft 24 so as to be rotatable in the width direction.
[0015]
The roll balance unit 15 is coupled so that the upper plate 20 and the outer shell 18 rotate about a roll shaft 21. Although not shown, the upper plate 20 is fixed to the printing apparatus side (pressing force applying mechanism) while maintaining the levelness. Plungers 22, 23 are disposed near both ends in the longitudinal direction of the upper plate 20 (see FIG. 6). The plungers 22 and 23 limit the rotation angle of the upper plate 20 and the outer shell 18 about the center of the roll shaft 21. Further, the plungers 22 and 23 are configured to limit the force (moment) of starting rotation by a built-in spring, and to be in a neutral state when the print head is not in contact with the mask 3.
[0016]
Two syringes 39 each containing a solder paste are attached to the rotating plate 19 in the longitudinal direction, and a hole larger than the diameter of the syringe 39 is formed in the outer shell 18 and the upper plate 20 so as not to contact the syringe 39. Is provided. The syringe 39 is covered with a syringe cap 40 having a hole 42 on the upper surface. The lower opening of the syringe 39 communicates with the closed space 41 of the closed part 1 through holes provided in the rotating plate 19, the jacket 14 and the inner shell 11.
<Operation description>
Next, the operation of the print head will be described with reference to FIGS. FIG. 3 is a cross-sectional view of the print head during a printing operation, and FIG. 4 is a schematic diagram illustrating the operation of the roll balance unit 15 with respect to the inclination of the substrate 4 and the mask 3.
[0017]
First, the substrate 4 carried into the printing machine is moved so as to have a desired positional relationship with the mask 3, and the upper surface of the substrate 4 and the lower surface of the mask 3 are brought into contact and fixed. Next, the print head is moved to a printing start position by a drive unit attached to the printing press. When compressed air is introduced into the holes 42 on the upper surface of the syringe cap 40 at the start of the printing operation, the solder paste 38 is supplied to the closed space 41. At this time, the amount of compressed air introduced into the hole 42 is controlled so that a predetermined amount of the solder paste 38 is supplied.
[0018]
The rotating plate 19 is provided with a paste sensor 43 (see FIG. 6). The paste sensor 43 measures the amount of the solder paste 38 in the closed space 41. When the capacity becomes less than or equal to the capacity, the supply of the solder paste is appropriately performed. As another method that does not use the paste sensor 43, there is a method in which the supply timing and the amount of the solder paste are set in advance from the time from the start of printing and the number of printed sheets.
[0019]
Next, the printing head is moved downward by the pressing force applying mechanism of the printing press main body connected to the driving unit 2 to come into contact with the mask 3 and further applies a pressing force. At this time, the air introduction holes 30 and 31 for operating the cylinder portions 16 and 17 for tilting the squeegees 7 and 8 back and forth with respect to the moving direction are open to the atmosphere.
[0020]
The cylinder section 16 includes a case 25, a holding plate 27, a piston 28, a piston lid 29, and a diaphragm 26 that provides elastic force. The outer periphery of the circular diaphragm 26 is sandwiched between the case 25 and the holding plate 27, and the center of the diaphragm 26 is sandwiched between the piston 28 and the piston lid 29 (see FIG. 3). The case 25 is fixed to the inner surface of the outer shell 18. The squeegees 7 and 8 are configured to be inclined forward or rearward by applying a force by the piston 28 being in close contact with the rotating plate 19.
[0021]
The space formed by the outer shell 18, the case 25 and the diaphragm 26 is sealed except for the air introduction holes 30 and 31 provided in the outer shell 18. After pressing against the mask 3 with a predetermined pressing force by the pressing force applying mechanism, compressed air is introduced from a compressor or the like into the space surrounded by the outer shell 18, the case 25 and the diaphragm 26 from the air introducing hole 30. The air introduction hole 31 of the opposed cylinder portion 17 is kept open to the atmosphere.
[0022]
Next, the diaphragm 26 pushes out the piston 28 to apply a counterclockwise rotating force to the rotating plate 19, and the pitch shaft 24 until the rotating plate 19 comes into contact with the stoppers 34 and 35 on the front side arranged on the outer shell 18. Rotate counterclockwise around. At this time, the piston 28 does not move linearly but moves in an arc trajectory. Further, by employing the structure using the diaphragm 26, problems such as galling of the shaft and the seal member, which occur in a normal cylinder, are prevented.
[0023]
Since the lower end of the squeegee 7 tends to move below the lower end of the squeegee 8 by the rotation of the rotating plate 19, the pressing force on the mask 3 is concentrated on the squeegee 7 as shown in FIG. Due to this curvature, the lower end of the squeegee 8 is kept in a state of lightly contacting the mask 3. All or a part of the side seals 12 and 13 are formed of an elastic material such as rubber or foamed polyethylene. Therefore, the state in which the side seal itself is in close contact with the mask 3 without any gap is maintained. For this reason, the tightness of the closed space 41 is ensured together with the front and rear squeegees 7 and 8.
[0024]
Next, in FIG. 3, when the print head is moved in the direction of the arrow (right), the solder paste 38 moves while rotating and fills the opening 6 of the mask 3. After the rear squeegee 7 has passed over all the openings 6, the print head is brought into close contact with the mask 3 and the substrate 4 and the mask 3 are peeled off, so that the solder paste 38 is formed on the conductor pattern 5 of the substrate 4. Transcribed. Printing in the opposite direction is performed according to the above procedure.
[0025]
Next, the operation of the roll balance unit 15 during the printing operation will be described with reference to FIGS. During the printing operation in FIG. 3, the reaction force against the pressing force from the squeegee 7 is so large that the reaction force from the squeegee 8 can be ignored. At this time, consider a case where the substrate 4 is tilted in a direction perpendicular to the moving direction (left-right direction in the figure) as shown in FIG. In this state, the driving unit 2 and the sealing unit 1 except for the roll balance unit 15 connected to the outer shell 18 rotate in the longitudinal direction around the roll shaft 21 due to the reaction force against the pressing force from the squeegee 7. Therefore, the pressing force at the lower end of the squeegee 7 becomes uniform in the longitudinal direction. Similarly, even when the lower ends of the front and rear squeegees are not parallel to the moving direction due to an attachment error or the like, the pressing force of the lower end of the rear squeegee becomes uniform in the longitudinal direction. At this time, the spring contained in the plunger 22 is compressed, but the reaction force is negligibly small compared to the reaction force of the pressing force.
[0026]
Therefore, even after the print head movement is completed, the print head is not lifted, and the deterioration of the internal solder paste 38 can be reduced in order to secure the sealed space 41 of the sealed portion 1. The mask 3 can be less damaged by opening to the atmosphere.
[0027]
In the present embodiment, a fluid passage groove 46 is provided between the jacket 14 and the inner shell 11, air adjusted to a predetermined temperature is flowed from the fluid introduction hole 47 through the fluid passage groove 46, and a fluid discharge hole 48 is provided. , The temperature of the solder paste 38 in the closed space 41 can be adjusted. It is conceivable to provide a temperature sensor in the closed space 41 to adjust the temperature of the fluid to be passed. However, it is possible to reduce the load on the print head by reducing the mass and wiring to the print head by flowing the air adjusted to be constant as in the present embodiment. Therefore, it is suitable. Furthermore, the fluid to be circulated is not limited to gas, but it is necessary to consider the effect at the time of outflow. The temperature of the solder paste 38 can also be adjusted by passing a temperature-controlled nitrogen gas or the like through the closed space 41. However, in that case, care must be taken to promote the evaporation of volatile components contained in the solder paste 38. It is desirable that the fluid discharged from the fluid discharge hole 48 be circulated again through the temperature controller or discharged at a position where the mask 3 is not dried, rather than being discharged as it is.
[0028]
In such a configuration, the jacket 14 needs to have heat insulation properties, and also needs mechanical strength and chemical resistance. Examples of such materials include high strength engineering plastics. As the material of the inner shell 11 and the squeegee holders 9 and 10, it is preferable to use aluminum having high thermal conductivity, excellent mechanical strength and chemical resistance, or anodized aluminum. It is more preferable to provide a heat radiation fin in order to enhance the heat radiation of the inner shell 11.
[0029]
As other methods, a method of adjusting the temperature of the inner shell 11 using a Peltier element or the like, or a method of disposing a Peltier element or the like inside the inner shell 11 and directly adjusting the temperature inside the sealed space 41 with a Peltier element or the like may be used.
[0030]
Further, a closed space including the closed portion 1 may be provided separately, and the temperature of the space may be adjusted. The volume of the closed space can be reduced if it is brought into contact with the mask 3 or the support member of the mask 3 or if it has a structure with a slight gap. In this case, the separately provided closed space may be configured to move with the print head, or may be configured to not move with the print head as long as the structure does not hinder the movement.
[0031]
FIG. 5 shows a state where the print head is moved up and down with the paste remaining on the mask portion. FIG. 5A shows a state in which the paste remains on the squeegee 7 side, FIG. 5B shows a state in which the print head is lifted in the state of FIG. 5A, and FIG. FIG. 5D shows a state in which the paste is separated from the squeegee, and FIG. 5D shows a state in which the print head is moved down so that the paste does not protrude.
[0032]
First, as shown in FIG. 5A, for some reason such as maintenance, the print head is raised after the printing operation. Then, as shown in FIG. 5B, the solder paste 38 attached to the squeegee 7 inside the closed space 41 and the solder paste attached to the mask 3 attract and extend. Thereafter, as shown in FIG. 5C, a part of the spread solder paste falls to the left side of the lower end of the squeegee 7. In this state, when the print head is lowered as it is, a part of the paste comes out of the closed space 41. Then, if left as it is, the protruding paste is dried and deteriorated.
[0033]
In the present embodiment, in order to prevent the above phenomenon, the print head shown in FIG. 5C is moved in the direction opposite to the printing direction (the direction of arrow P) before being lowered, and then lowered. It is appropriate that the distance moved in the opposite direction is about half the distance between the lower end of the squeegee 7 and the lower end of the squeegee 8. This movement operation may be performed until the descent is completed, and may be performed when the descent is performed.
[0034]
The supply of the solder paste 38 at the start of the printing operation can be performed by the following method. That is, before the print head is brought into contact with the mask 3, a solder paste 38 is supplied onto the mask 3 with a spatula or the like. In this case, when the squeegees 7 and 8 come into contact with the mask 3, it is necessary that the solder paste 38 be contained in the closed space 41 of the closed portion 1. When this is used, the syringe 39 and the like are not required, and the configuration can be simplified.
[0035]
Further, as a method of supporting the contact portion 1 for rotation in the front-rear direction of the traveling direction, an actuator having another configuration capable of performing a rotation operation may be used. For example, it may be rotated by a combination of a double-acting cylinder and a shaft capable of pushing and retracting, and a mechanism for preventing galling of the seal member. The effect is the same even if a rotating actuator such as a motor is used.
[0036]
The sealing unit 1 and the driving unit 2 of the present embodiment are connected by the mounting screws 32 using the holes provided on the rotating plate 19 and the screw holes 33 provided on the jacket 14, so that the sealing unit 1 and the driving unit 2 can be easily removed, and Exchange is possible. The easy removal is effective at the time of maintenance such as replacement of a squeegee, and the type of the solder paste corresponding to the type of the substrate 4 to be printed by replacing the sealing portion 1 can be changed in a short time. Furthermore, by preparing several kinds of sealing portions 1 having different dimensions, it is possible to change the size according to the size of the substrate 4. As a result, the amount of solder paste supplied to the sealing portion 1 can be minimized, and the consumption of solder paste can be reduced.
[0037]
As shown in FIG. 6, the rotating plate 19 is provided with a solvent concentration sensor 44. This concentration sensor monitors the concentration of the solvent component used in the solder paste in the closed space. When the concentration sensor 44 detects that the concentration of the solvent component has fallen below an arbitrary set value, the solvent component used in the solder paste is supplied from the solvent supply hole 45 to the closed space 41, so that the inside of the solder paste is removed. Can suppress the evaporation of the solvent, or can replenish the insufficient solvent component. When this solvent component is supplied in a liquid state, the components of the solder paste 38 become non-uniform, and the printing result tends to be uneven. Therefore, it is better to supply air containing a mist or a high-concentration solvent. Alternatively, the supply timing and amount of the solvent may be defined based on the time from the start of printing and the number of printed sheets without using the solvent concentration sensor. Further, when supplying the solder paste from the syringe 39, a similar effect can be obtained by supplying a solder paste having an increased solvent content.
[0038]
Note that a roll mechanism for roll balance may be provided for each of the front and rear squeegees to correct the roll direction. However, unless the roll mechanism is configured to move in combination with the drive unit, the squeegee on the front side in the advancing direction vibrates due to friction, and pitching occurs, resulting in poor printing results.
[0039]
As described above, according to the print head and the printing method according to the present embodiment, separately from the sealed portion provided with the squeegee or the like, a mechanism for applying a rotational force in the front-rear direction with respect to the print head advancing direction is provided on the drive unit side. And a mechanism for applying a rotational force in a direction perpendicular to the direction. As a result, a large pressing force can be applied to the squeegee on the rear side in the traveling direction of the print head at the time of printing, and the front squeegee can maintain the airtightness without being separated from the mask, thereby achieving good printing. realizable.
[0040]
【The invention's effect】
As described above, according to the print head and the printing method using the print head of the present invention, deterioration can be reduced because the paste is always placed in the closed space even during the printing operation. . In addition, since the printing is performed in a state where the pressing force at the lower end of the squeegee is uniform in the longitudinal direction, good printing can be stably performed over a long period of time.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a print head according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a print head according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a print head showing a pitching correction operation during a printing operation according to the present invention.
FIG. 4 is a schematic diagram illustrating a rolling correction operation of the print head of the present invention.
FIG. 5 is a diagram illustrating a state of the paste when the print head is moved up and down while the paste remains on the squeegee.
FIG. 6 is a longitudinal sectional view of the print head of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sealing part, 2 ... Drive part, 3 ... Mask, 4 ... Substrate, 7 ... Squeegee, 8 ... Squeegee, 11 ... Inner shell, 12 ... Side seal, 13 ... Side seal, 15 ... Roll balance part, 18 ... Outside Shell, 26: diaphragm, 32: screw, 38: solder paste, 41: closed space, 42 holes.

Claims (5)

A mask having an opening on the substrate is fixed, and a pair of squeegees for transferring a paste onto the substrate through the opening of the mask are provided on the outer shell of the printing head. a squeegee, a sealing portion disposed on the both ends of the pair of squeegee, a sealing portion for sealing the space surrounded by the squeegee and the seal portion and the mask, a rotating plate provided inside of the outer shell, the sealing A drive mechanism provided with a pitch mechanism for rotating the unit in the front-rear direction with respect to the movement direction, and a roll mechanism for rotating the sealing unit in a direction perpendicular to the movement direction, wherein the pitch mechanism includes the outer shell. And a piston that is provided so as to substantially oppose the rotating plate and applies a rotational force to rotate the rotating plate, and is provided on the outer shell and the longitudinal end side of the rotating plate, and is on the front side with respect to the moving direction. S Print head, characterized in that it comprises a plurality of stoppers for limiting the pitching direction of displacement of the over-di. The print head according to claim 1, wherein the sealing unit and the driving unit are fastened with a screw. 3. The print head according to claim 1, further comprising a mechanism for supplying a solvent into the closed portion. The print head according to any one of claims 1 to 3, further comprising a temperature adjustment mechanism for adjusting a temperature of a space in the sealed portion. A printing method using a print head having a squeegee provided on an outer shell for fixing a mask having an opening on a substrate and transferring a paste onto the substrate through the opening of the mask, provided before and after the moving direction. A pair of squeegees, a paste is supplied to a sealed space formed by a seal portion and a mask provided at both ends of the squeegee, and the paste is provided so as to be substantially opposed between the outer shell and the rotating plate. Including a piston for applying a rotating force to rotate, and a plurality of stoppers provided on an outer shell and a longitudinal end side of the rotating plate for limiting a displacement amount of a front stage in a pitching direction with respect to a moving direction. pitch mechanism, as the pressing force in the moving direction front portion of the rear squeegee mask than the squeegee is increased, along with rotating the sealed space in the moving direction, the longitudinal direction of the squeegee before and after Printing method and performing printing operation while applying a rotational force to be substantially parallel.

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