JP5128171B2 - Screen printing device - Google Patents

Description

  The present invention relates to a screen printing apparatus for printing a solder paste on a substrate.

In the field of mounting electronic components on a board, a screen printing apparatus is widely used as an apparatus for printing a solder paste on an electrode of the board. This apparatus includes a mask having a pattern hole corresponding to the shape of the electrode, and fills the pattern hole of the mask superimposed on the substrate with the solder paste to print the solder paste on the electrode. In the screen printing apparatus, the plate separation work is performed in the final printing process, and the printed substrate and the mask are separated from each other. In this plate separation, a part of the solder paste is placed on the edge of the pattern hole. In some cases, the residual solder paste gradually accumulates as printing is repeated, causing clogging of the pattern holes. In addition, the solder paste may leak from the pattern hole due to the reason that the filling pressure at the time of filling is too high, and the back surface of the mask (the surface in contact with the substrate) and the substrate may be soiled. If the solder paste remains on the pattern hole or the back side of the mask in this way, printing defects such as substrate contamination or insufficient printing amount occur. Measures such as mask cleaning for wiping off the solder paste remaining on the substrate are taken (see Patent Document 1).
Japanese Patent Laid-Open No. 9-323402

  Conventionally, the timing at which mask cleaning is performed can be set to an arbitrary interval such as every predetermined work time or every time a predetermined number of substrates are printed. However, the degree of residual solder paste is affected by a variety of factors such as the type of solder paste, mask material, thickness, pattern hole shape, printing temperature and humidity, etc. It was difficult to do. If the interval is short, the mask can be maintained in a clean state, so that the printing quality is stable, but the printing operation must be interrupted during the cleaning, which leads to a deterioration in production tact. On the other hand, if the interval is long, it is advantageous in terms of production tact, but the printing operation is performed in a state where the solder paste remains, resulting in variation and deterioration in printing quality. Further, the interval set also varies depending on individual differences among operators who perform printing work, and it has been difficult to maintain stable print quality under various conditions with a single screen printing apparatus.

  Therefore, an object of the present invention is to provide a screen printing apparatus that performs mask cleaning at an appropriate timing.

The screen printing apparatus according to claim 1 is a screen printing apparatus that prints a solder paste on a substrate through a pattern hole provided in a mask for masking the substrate, and solders the pattern hole provided in the mask for masking the substrate. A filling means for filling a paste; a mask for filling the pattern hole with a solder paste; a plate separating means for separating the substrate; and a measuring means for measuring a deflection amount generated in the mask at the time of separating the plate; A removing means for removing the solder paste remaining on the mask; and a judging means for determining the necessity of removing the solder paste based on the amount of deflection measured by the measuring means . The substrate in contact with the back surface is lowered to separate the mask from the substrate, and the measuring means contacts the back surface of the mask. Further, the amount of deflection of the mask is measured from the difference between the height of the mask before the substrate starts to descend and the height of the mask while the substrate is descending, and the determination means subtracts a certain amount of deflection. If the amount of bending is further confirmed, it is determined that the mask needs to be removed of the solder paste .

A screen printing apparatus according to a second aspect is the screen printing apparatus according to the first aspect, wherein the measuring means is horizontally movable and measures the height of the mask at an arbitrary position .

  According to the present invention, the necessity of mask cleaning is determined based on the amount of deflection of the mask at the time of separating the plate, which changes according to the degree of mask contamination due to residual solder paste. It can be performed.

  A screen printing apparatus according to an embodiment of the present invention will be described. FIG. 1 shows the overall configuration of the screen printing apparatus.

  The screen printing apparatus 1 includes a mask 3 having a pattern hole 3a corresponding to the electrode shape of the substrate 2, mask support means for supporting the outer periphery of the mask 3 at a predetermined height, and supporting the substrate 2 from both sides. A substrate-side support means, a substrate transport means for transporting the substrate 2, a substrate lower support means for supporting the substrate 2 from below, a substrate lifting means for lifting and lowering the substrate 2 to and from the mask 3, and a substrate 2 A substrate moving means for moving and aligning with respect to the mask 2; a filling means for filling the pattern hole 3a of the mask 3 with a solder paste; a removing means for removing the solder paste remaining on the mask 3; It comprises measuring means for measuring the amount of displacement of the mask 3 toward the substrate 2 before and after, and control means for controlling the operation of these means.

  In FIG. 1, the mask support means includes a mask support block 4 that supports the outer periphery of a thin plate-like mask 3, and supports the mask 3 at a predetermined position and height.

  The substrate transport means includes a pair of transport rails 10 for mounting both sides of the substrate 2 and transports the substrate 2 by a built-in belt conveyor or the like.

  The substrate lower support means includes a substrate support block 11, a table 12 on which the substrate support block 11 is installed, a feed screw 13 for moving the table 12 up and down, a motor 14, and rotational driving of the motor 14. The belt 15 is transmitted as a rotation, and the substrate support block 11 is brought into contact with the lower surface of the substrate 2 by the operation of the motor 14 and is raised to a predetermined height.

  The substrate-side support means includes a pair of clamp plates 16a and 16b that sandwich the substrate 2 from both sides, and an actuator 17 that contacts and separates one clamp plate 16a from the other clamp plate 16b. The position of is temporarily fixed.

  The substrate elevating means includes a support block 18, a table 19 provided with the support block 18, a feed screw 20 for moving the table 19 up and down, a substrate elevating motor 21, and a rotational drive of the substrate elevating motor 21. The support block 18 supports the pair of transport rails 10 and the clamp plate 16. The operation of the substrate lifting motor 21 causes the substrate 2 to move up and down below the mask 3, and during printing, the substrate 2 is raised until it abuts against the mask 3, and after printing, the substrate 2 is lowered to separate the substrate 2 and the mask 3 from each other. .

The substrate moving means rotates the substrate 2 sandwiched between the pair of clamp plates 16 in the X and Y directions orthogonal to each other in the horizontal plane, and further in the θ direction around the Z direction (vertical direction), the Y table 24, The θ table 25 is laminated, and the substrate 2 is freely moved with respect to the mask 3 fixed at a predetermined position for alignment. In this alignment, marks provided as alignment references on the substrate 2 and the mask 3 are imaged by the cameras 5a and 5b, respectively, and the positional relationship between the substrate 2 and the mask 3 is recognized.

  The filling means includes a pair of squeegees 26 a and 26 b, squeegee lifting cylinders 27 a and 27 b that lift and lower the squeegees 26 a and 26 b independently, and a pair of squeegees 26 a and 26 b that move horizontally along the surface of the mask 3. The screw 28 and a squeegee moving motor 29 for rotating the feed screw 28 are included. When printing the solder paste, only one squeegee 26a is slid on the surface of the mask 3, and the solder paste is filled into the pattern hole 3a from one direction. As a result, printing of the solder paste on the substrate 2 is completed, and for the new substrate 2, only the other squeegee 26b is slid on the surface of the mask 3, and the solder paste is filled into the pattern holes 3a from the opposite direction. Thus, each time a new substrate 2 is carried in, the pair of squeegees 26a and 26b are alternately slid on the surface of the mask 3 to fill the solder paste.

  The removing means is composed of a mask cleaner 6 that horizontally moves along the back surface of the mask 3. The mask cleaner 6 is provided with a cleaning paper 6a wound around a roller 6a, and the cleaning paper 6a is slid on the back surface of the mask 3 to remove the solder paste remaining on the mask 3. Since the removal capability of the cleaning paper 6a to which the removed solder paste is attached is lowered, the cleaning paper 6a is wound around the winding roll 6c so that a new portion always comes into contact with the back surface of the mask 3.

  In the screen printing apparatus 1 configured in this way, only the outer periphery of the mask 3 is supported by the mask support block 4, so that the center portion away from the mask support block 4 is likely to be bent. Therefore, when the plate is released, the central portion of the mask 3 tends to bend downward toward the substrate 2 due to the viscosity of the solder paste filled in the pattern hole 3a. When the mask is dirty, for example, when the residual solder paste is deposited on the edge of the pattern hole 3a as a result of repeated printing, or when the solder paste adheres to the back surface of the mask 3 The mask 3 and the substrate 2 are more strongly bonded to each other, and the deflection generated in the mask 3 at the time of separating the plate tends to increase. Therefore, it is possible to determine the degree of contamination of the mask 3 by measuring the amount of deflection generated in the mask 3 when the plate is released.

  FIG. 2 is a block diagram showing a control configuration related to mask cleaning. The control unit 30 is a control unit that performs operation control of each of the above-described units constituting the screen printing apparatus 1. The mask measuring unit 31 is a measuring unit that measures the amount of deflection generated in the mask 3 when the plate is separated using the laser measuring device 32. As shown in FIG. 3, the laser measuring device 32 irradiates laser light vertically downward from above the mask 3 toward the surface of the mask 3, and based on the position where the reflected light from the surface of the mask 3 is received. , Here, the distance from the laser measuring device 32 to the surface of the mask 3 is measured. As shown in FIG. 3A, for example, the laser measuring device 32 finishes filling the pattern hole 3a of the mask 3 with the solder paste before starting the plate separation, and the substrate 2 starts to descend for the plate separation. The height measurement of the mask 3 is started at the timing, and the measurement is continued even while the substrate 2 is lowered as shown in FIG. The difference between the height of the mask 3 before the substrate 2 starts to descend and the height of the mask 3 that is descending becomes the deflection amount a of the mask 3 when the plate is released. The amount of deflection measured in this way includes a certain amount of deflection that occurs even when the mask 3 is not soiled, so if the amount of deflection is confirmed even after subtracting this, It can be determined that the mask 3 is dirty with the residual solder paste. The start timing of the lowering operation of the substrate 2 is transmitted to the mask measurement unit 31 from the drive unit 33 that is a drive driver of the substrate lifting motor 21.

The mask cleaning determination unit 34 is a determination unit that determines the degree of contamination according to the amount of deflection of the mask 3 and determines the necessity of mask cleaning. Specifically, an amount of deflection due to contamination of the mask 3 to an acceptable level is set in advance, and the necessity of mask cleaning is determined using the amount of deflection as a threshold value. That is, when the amount of deflection of the mask 3 measured by the mask measuring unit 31 exceeds the threshold, it is determined that unacceptable contamination has occurred, it is determined that mask cleaning is necessary, and the threshold is satisfied. If not, it is determined that the mask 3 is not dirty or is acceptable even if it is dirty, and it is determined that mask cleaning is unnecessary. When it is determined that mask cleaning is necessary, a cleaning start command is issued to the mask cleaner 6 and the pair of clamp plates 16 and the like are lowered to a height that does not interfere with the mask cleaner 6.

  The laser measuring device 32 is not particularly limited as long as it is a position where the height of the mask 3 can be measured at the time of separating the plate, but when installed between the pair of squeegees 26a and 26b as shown in FIG. There is an advantage that the height of the mask 3 can be measured at an arbitrary position because the movable motor 29 can be driven to move horizontally above the mask 3. This is because there are a wide variety of masks 3 used in the screen printing apparatus 1, and the number and form of the pattern holes 3a are different as well as their shapes, so it is more possible to change the measurement position according to the situation. This is because the amount of deflection of the mask 3 can be accurately measured.

  FIG. 4 is a flowchart showing the printing operation in the screen printing apparatus 1. After printing on a plurality of substrates (N-1) in the screen printing apparatus 1, the Nth substrate is carried in by the substrate transport means (ST1). The substrate is supported from below by the substrate lower support means, and the substrate is supported from both sides by the substrate side support means and temporarily fixed, and is lifted by the substrate lifting means and brought into contact with the back surface of the mask. Solder paste is filled into the pattern holes of the mask by the paste filling means (ST2). When the filling of the solder paste is completed, the substrate is lowered by the substrate raising / lowering means and separated from the mask (ST3). When the plate is released, the amount of deflection of the mask is measured by the measuring means (ST4). If the amount of deflection of the mask exceeds the threshold value, mask cleaning is performed (ST5). When the amount of deflection of the mask is less than the threshold value and after the mask cleaning, the next substrate (N + 1th sheet) is newly carried in and printing is performed.

  As described above, according to the screen printing apparatus of the present embodiment, the necessity for mask cleaning is determined based on the amount of deflection of the mask at the time of separating the plate, which changes according to the degree of contamination of the mask by the residual solder paste. Conventionally, the mask cleaning, which has been performed every fixed printing time or every certain number of processed substrates, can be performed at the timing when the mask is actually dirty, regardless of the degree of mask contamination. As a result, it becomes possible to perform mask cleaning at intervals where there is no excess or deficiency, and it is possible to achieve both improvement in print quality and productivity that are in a trade-off relationship.

  According to the present invention, the necessity of mask cleaning is determined based on the amount of deflection of the mask at the time of separating the plate, which changes according to the degree of mask contamination due to residual solder paste. And is useful in the field of electronic component mounting.

Front view of a screen printing apparatus according to an embodiment of the present invention The block diagram which shows the control structure regarding the mask cleaning in the screen printing apparatus of embodiment of this invention. The figure which shows the measuring method of the deflection amount of the mask at the time of plate separation in the screen printing apparatus of embodiment of this invention 7 is a flowchart showing a printing operation in the screen printing apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screen printing apparatus 2 Board | substrate 3 Mask 3a Pattern hole 6 Mask cleaner 18 Support block 19 Table 20 Feed screw 21 Board | substrate raising / lowering motor 22 Belt 26a, 26b Squeegee 27a, 27b Squeegee raising / lowering cylinder 28 Feed screw 29 Squeegee moving motor 30 Control part 31 Mask Measuring unit 32 Laser measuring device 34 Mask cleaning judgment unit

Claims (2)

A screen printing apparatus for printing a solder paste on a substrate through a pattern hole provided in a mask for masking the substrate,
A filling means for filling a pattern hole provided in a mask for masking the substrate with a solder paste; a mask for filling the pattern hole with a solder paste; and a plate separating means for separating the substrate from the plate; Measuring means for measuring the amount of deflection generated in the mask, removing means for removing the solder paste remaining on the mask, and determination for determining the necessity of removing the solder paste based on the amount of deflection measured by the measuring means With means ,
The plate separating means lowers the substrate in contact with the back surface of the mask to separate the mask and the substrate;
The measuring means measures the amount of deflection of the mask from the difference between the height of the mask before the substrate contacting the back surface of the mask starts to descend and the height of the mask while the substrate is descending;
The screen printing apparatus according to claim 1, wherein the determination unit determines that the mask needs to remove the solder paste when the amount of bending is further confirmed even after a certain amount of bending is subtracted . The screen printing apparatus according to claim 1, wherein the measuring unit is horizontally movable and can measure the height of the mask at an arbitrary position .

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