JP3139259B2 - Screen printing method of cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing method of cream solder for applying cream solder for soldering electronic components to a printed circuit board.

[0002]

2. Description of the Related Art Prior to surface mounting electronic components such as ICs, LSIs, capacitor chips, and resistor chips on a printed circuit board, a cream for soldering the electronic components to electrodes of a circuit pattern on the printed circuit board by a screen printing apparatus. Solder is applied.

[0003] This type of screen printing apparatus generally has a screen mask by sliding a squeegee over the screen mask, as shown in, for example, Japanese Patent Application Laid-Open No. 4-65243. The cream solder is applied to a predetermined portion of the printed circuit board through the pattern hole formed in the substrate.

FIG. 4 is a front view of a conventional screen printing apparatus, showing a state where cream solder is applied to a printed circuit board by the conventional screen printing apparatus.
The screen mask 1 is configured by mounting a mask plate 2 on the lower surface of a frame-shaped holder 3. Printed circuit board 4
Are held on the table 5. Nuts 6a, 6b are mounted on both sides of the table 5, and the nuts 6a,
Vertical feed screws 7a and 7b are screwed into 6b. One feed screw 7a is driven by a motor 8 to rotate. Timing pulleys 9a and 9b are mounted on the feed screws 7a and 7b, and a timing belt 10 is adjusted on the timing pulleys 9a and 9b. 11 is a feed screw 7b
Bearing.

When the motor 8 is driven, one of the feed screws 7a
Rotates, and this rotation is transmitted to the other feed screw 7b via the timing pulleys 9a and 9b and the timing belt 10, and both the feed screws 7a and 7b rotate at the same time. 2
To go up and down. Reference numeral 12 denotes a squeegee that slides on the mask plate 2, and reference numeral 13 denotes cream solder applied to the printed circuit board 4.

Next, the operation will be described. The motor 8 is rotated forward to raise the printed circuit board 4, and the upper surface of the printed circuit board 4 is brought into contact with the lower surface of the mask plate 2. Next, when the squeegee 12 is slid to the left on the mask plate 2 by a driving means (not shown), the cream solder 13 is applied to the upper surface of the printed circuit board 4 through a pattern hole (not shown) formed in the mask plate 2. Is done. Next, by reversely rotating the motor 8, the printed circuit board 4 is lowered and separated from the mask plate 2, and the application process of the cream solder 13 is completed.

[0007]

Conventionally, when the cream solder 13 is applied as described above, a slight gap (generally called "snap-off") is secured between the mask plate 2 and the upper surface of the printed circuit board 4. It had been. However,
As the pitch of electronic component leads becomes increasingly narrower,
The snap-off has been gradually reduced, and in recent years, the snap-off has become zero, and the cream solder 13 is applied by bringing the upper surface of the printed circuit board 4 into contact with the lower surface of the mask plate 2.

However, the upper surface of the printed circuit board 4 is brought into contact with the lower surface of the mask plate 2 so that the
When the coating 3 is applied, there is a problem that the cream solder 13 applied to the printed board 4 is easily deformed when the printed board 4 is lowered and separated from the mask plate 2. Next, the reason why the shape collapse occurs will be described with reference to FIG. FIGS. 5A to 5C are explanatory diagrams of the operation of the conventional screen printing apparatus.

FIG. 5A shows a state immediately after the application of the cream solder after the sliding of the squeegee 12 is completed. The cream holes 13 are filled in the pattern holes of the mask plate 2 by sliding the squeegee 12, and the lower surface of the mask plate 2 is adhered to the upper surface of the printed circuit board 4 due to the adhesive force. Next, when the printed board 4 is lowered by rotating the motor 8 in the reverse direction, the mask plate 2 is gradually bent downward by its own elasticity because it is stuck to the printed board 4 (see FIG. 5B). When the printed circuit board 4 is further lowered, the mask plate 2 is peeled off from the printed circuit board 4 at a stretch as shown in FIG. 5C, and returns to a horizontal state shown by a solid line in FIG.
Incidentally, the mask plate 2 is formed of a flexible metal thin plate having elasticity such as a stainless steel plate.

As described above, when the printed board 4 is lowered to separate the printed board 4 from the mask plate 2, the mask plate 2 is immediately removed from the printed board 4 by its own elasticity when the printed board 4 is lowered to some extent. As a result, the cream solder 13 in the pattern hole is disturbed by the impact at that time, and the plate removability is deteriorated and the shape of the cream solder 13 on the printed circuit board 4 is lost.

FIG. 6 shows a typical shape of the cream solder 13 transferred to the printed circuit board 4. The cream solder 13a on the left is a non-defective product, and the cream solder 13b on the right is a defective product that has been deformed for the above-described reason. In this example, the edge portion thereof unnecessarily protrudes upward. Depending on the cream solder 13b that has been deformed as described above, it is difficult to correctly solder the leads of the electronic component. Such deterioration of the print-out property is remarkable when applying the cream solder at a fine pitch by the fine-pitch pattern holes, and is particularly problematic when electronic components having narrow pitch leads are surface-mounted on a printed circuit board. Become.

In the above conventional example, a screen printing apparatus which raises and lowers the printed circuit board 4 with respect to the screen mask 1 has been described as an example. The same problem occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cream solder screen printing method capable of preventing the shape of the cream solder from being lost when the printed board and the mask plate are separated.

[0014]

According to the present invention, there is provided a screen printing method for cream solder, the lower surface of which is sucked by a suction block.
The printed circuit board into contact with the lower surface of the mask plate.
By sliding the squeegee on the scoop
Cream half that prints cream solder on the upper surface of the printed circuit board
Screen printing method for squeegees
And slide it on the top of the printed circuit board.
After printing, the lower surface of the mask plate
The squeegee is received by the
To lower the suction block while biasing it
The substrate is separated from the mask plate .

[0015]

[Action] Oite to the configuration described above, under the mask plate receiving portion
And urged the squeegee to the mask plate
By lowering the suction block in this state, the mask
The rate does not fluctuate up and down.
The plate is released while being held in a substantially parallel state.
The cream solder is printed on the printed circuit board without
Is applied to the plate with good removability.

[0016]

[0017]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 4 to 4 show a conventional screen printing apparatus.
Components that are the same as the components in FIG. 6 are given the same reference numerals, and descriptions thereof are omitted. FIG. 1 is a perspective view of a screen printing apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 14 denotes a base, and reference numeral 20 denotes a board positioning unit provided on the base 14 for positioning the printed circuit board 4. The substrate positioning unit 20 will be described later in detail with reference to FIG. Reference numeral 60 denotes a magazine for accommodating different types of screen masks 1 in upper and lower stages.
Is operated when the lift motor 62 is operated.
It is a lifter that raises and lowers 0. 70 is a screen mask 1 at a predetermined height among the screen masks 1 in the magazine 60 shown in FIG.
And a mask pull-out portion that pulls out in the direction of arrow M1 or conversely moves in the direction of arrow M2 and returns the inside of the magazine 60. Of the mask pull-out portions 70, 71 and 72 are mask guides supported by columns 73 erected on the base 14 so as to be opposed to each other in the Y-direction. On the opposite side, the screen mask 1 is moved in the Y direction by moving means (not shown).
On the opposite side, a feed screw 75 that extends in the Y direction and is rotated by a motor 71a is rotatably supported on the opposite side, and the feed screw 75 has two squeegees. A support plate 77 for supporting the lifting / lowering 12
A feed nut 76 integrally connected with the screw is screwed.
The support plate 77 is slidably mounted on the upper surfaces of the mask guides 71 and 72 in the Y direction. Therefore, when one of the cylinders 78 is driven to lower one of the squeegees 12 and the motor 71a is driven, the mask plate 2
On the squeegee 12, move the squeegee 12 in the direction of arrow M1 or arrow M
It can be slid in two directions.

Next, the substrate positioning unit 20 will be described with reference to FIG. FIG. 2 is a front view of a substrate positioning unit of the screen printing apparatus according to one embodiment of the present invention. In FIG. 2, reference numeral 21 denotes an X table, which is mounted on the base 14 as shown in FIG.
Is a Y table placed on the X table 21 and driven by the Y motor 24. Reference numeral 25 denotes a first feed screw rotatably supported by a plate 23a mounted on the Y table 23, and reference numeral 26 denotes a second feed screw which is similarly supported and has the same thread portion as the first feed screw 25. It is a screw. First
A timing pulley 27 and a timing pulley 28 are respectively mounted on the lower portions of the feed screw 25 and the second feed screw 26, and a timing belt 29 is tuned to the timing pulley 27 and the timing pulley 28. A feed nut 30 rotatably supported by the first lift plate 31 so as to be unable to move up and down is screwed to the upper portions of the first feed screw 25 and the second feed screw 26. Further, the first Z screw 3 fixed to the lower surface of the plate 23a is connected to the first feed screw 25.
2 is transmitted via the gear train 33. Therefore, when the first Z motor 32 is driven, the first feed screw 25 and the second feed screw 26 can be rotated via the gear train 33, the timing pulley 27, the timing belt 29, and the timing pulley 28. Thus, the first lift plate 31 moves up and down in the direction of arrow N1. In the present embodiment, the first Z motor 32,
The gear train 33, the timing pulley 27, the timing belt 29, the timing pulley 28, the first feed screw 25, and the second feed screw 26 correspond to the contact means.

The first lift plate 31 has a lift guide 34,
An elevating guide 35 is erected, and a first block 36 is fixed above the elevating guide 34.
A second block 37 is fixed to an upper part of the fifth block 5. A clamper 38 slidable in the direction of arrow N3 is provided above the first block 36. The upper surface of the clamper 38 and the upper surface of the second block 37 have a function as a lower receiving portion of the mask plate 2 and are at the same level. A slide cylinder 39 is fixed to the left side of the first block 36 in FIG. 2 so that the rod 40 faces leftward in FIG. 2 is connected to the left part of FIG. Therefore, when the slide cylinder 39 is driven to push and retract the rod 40, the clamper 38 can be moved in the direction of the arrow N3, whereby the printed circuit board 4 existing between the clamper 38 and the second block 37 can be moved. Can be clamped so as to be able to freely contact and separate. That is, the clamper 38 and the second block 37
Corresponds to the clamping means. In addition, at a portion where the first block 36 and the second block 37 face each other,
A conveyor 42 and a conveyor 43 for transporting the printed circuit board 4 in a direction perpendicular to the paper surface of FIG. 2 are provided.

A second elevating plate 44 is guided by the elevating guide 34 and the elevating guide 35 via a bearing 45 so as to be able to ascend and descend in the direction of arrow N2. A feed nut 46 is rotatably supported by the first elevating plate 31. It is pivoted. A second Z motor 47 for rotating the feed nut 46 is fixed to a lower portion of the first elevating plate 31 via a gear train 48, and an upper portion of the feed nut 46 is supported by a bearing 50 on the second elevating plate. 44
A third feed screw 49 that is rotatably supported by the first screw is screwed. Further, a suction block 51 provided with a suction pipe 52 for sucking the lower surface of the printed circuit board 4 is fixed to a position on the upper surface of the second elevating plate 44 directly below the printed circuit board 4. Therefore, the second Z motor 4
7, the feed nut 46 and the third feed screw 49 can be rotated via the gear train 48, whereby the second lift plate 44 and the suction block 51 are moved relative to the first lift plate 31. To move up and down in the direction of arrow N2. As described above, in the present embodiment, the second Z motor 4
7, gear train 48, third feed screw 49, feed nut 46
Corresponds to the suction block elevating means.

The control unit 90 controls the slide cylinder 39, the first Z motor 32, the X motor 22, the second Z motor 47, and the Y motor 24. In the control unit 90, 91 is a ROM (Read Only Memory) storing a control program according to the operation patterns shown in FIGS. 3A to 3E, 92 is a control program of the ROM 91, and is a slide cylinder. 39, the first Z motor 32, X
It is a CPU (Central Processing Unit) that gives an operation command to a driver 93 that operates the motor 22, the second Z motor 47, and the Y motor 24. In the control program of the ROM 91, the second block 37 and the clamper 38 receive the mask plate 2 and the printed circuit board 4 and the mask plate 2 are restrained in a parallel state.
7, the printed board 4 is separated from the mask plate 2 by acceleration control. 94 is R
The RAM 94 is an AM (random access memory), and stores data relating to the size of the printed circuit board 4 and other necessary data.

Next, each process of the above-mentioned operation pattern will be described with reference to FIG. Here, as shown in FIG. 3A, a new mask plate 2 is pulled out from the magazine 60 and set, and the description will be made from the point when the loading of the printed circuit board 4 by the conveyors 42 and 43 is completed. In the state shown in FIG. 3A, the mask plate 2 is
4. When pulling out of the magazine 60 by the clamp 4, the clamper 38,
The level of the clamper 38 and the second block 37 is lower than the level of the mask plate 2 so that the second block 37 and the holder 3 do not interfere with each other. In order to prevent the printed board 4 and the suction block 51 from interfering with each other when the printed board 4 is carried in, the upper surface of the suction block 51 is positioned lower than the lower surface of the printed board 4. 40 is projected,
The clamper 38 is at a position where the printed circuit board 4 is not clamped.

When the loading of the printed circuit board 4 is completed, as shown in FIG. 3B, while the mask plate 2 is not in contact with the clamper 38 and the second block 37, the CPU 92 sets the second Z. The motor 47 is driven to raise the suction block 51 as indicated by the arrow N4. As a result, the printed circuit board 4 is moved to the conveyor 42 and the conveyor 43.
Then, the lower surface is moved to a state where the lower surface is sucked by the upper surface of the suction block 51 and rises. Then, the upper surface of the clamper 38 and the second block 37 and the printed circuit board 4
When the upper surface becomes flush (at the same level), the lifting of the suction block 51 is stopped. The thickness of the printed circuit board 4 is known, and is stored in the RAM 94 as data. Then, when the printed circuit board 4 is flush with the clamper 38 and the second block 37, the CPU 92 drives the slide cylinder 39 to immerse the rod 40 in the direction of arrow N5. As a result, the printed circuit board 4 is clamped by opposing sides of the clamper 38 and the second block 37. At about the same time, suction is performed by suction means (not shown) connected to the suction pipe 52, and the lower surface of the printed circuit board 4 is suctioned to the upper surface of the suction block 51.

Next, while maintaining the clamped state shown in FIG. 3B, the CPU 92 drives the first Z motor 32 to move the clamper 38, the printed board 4, and the second block 37 together with the first elevating plate 31. The lifting is stopped when the upper surface of the clamper 38, the printed board 4, and the second block 37 contacts the lower surface of the mask plate 2. As a result, the lower surface of the mask plate 2 is received by the clamper 38 and the upper surface of the second block 37 at a position immediately beside the printed board 4, so that the mask plate 2 cannot be lowered around the printed board 4. Of course, at this time, the upper surface of the printed circuit board 4 is in contact with the lower surface of the mask plate 2. Then, as shown by arrows N7 and N8 in FIG. 3C, the cylinder 78 is driven so that the lower edge of one of the squeegees 12 is brought into contact with the mask plate 2 and the motor 71a is driven.
Is driven, and the cream solder 13 is applied by the squeegee 12.

Next, when the application of the cream solder 13 is completed, as shown in FIG. 3D, the CPU 92 drives the slide cylinder 39 to cause the rod 40 to protrude in the direction of arrow N9, and the printing by the clamper 38 is performed. The clamp on the substrate 4 is released. Then, the CPU 92 sets the second Z motor 4
7 is driven by acceleration control, and the suction block 51 for sucking the printed circuit board 4 is gradually increased in speed from zero to be lowered, thereby separating the mask plate 2 from the printed circuit board 4. At this time, since the printed circuit board 4 is sucked by the suction block 51, the printed board 4 is maintained in a horizontal posture, and the mask plate 2 is received by the clamper 38 and the upper surface of the second block 37, and the mask plate 2 is received as shown in FIG. As shown by the broken line, the mask plate 2 is urged toward the mask plate 2 by the printing pressure f of the squeegee 12, so that the mask plate 2 does not swing up and down. As described above, since the plate separation is performed while the printed board 4 and the mask plate 2 are restrained in a substantially parallel state, FIG. 5B or 5C showing the conventional technique.
As shown in (2), the mask plate 2 does not vibrate greatly in the vertical direction, and the cream solder 13 does not collapse. In addition, the lowering speed of the suction block 51 is gradually increased by acceleration control, so that the mask plate 2 and the printed circuit board 4 do not separate from each other at once, and the shape of the cream solder 13 is further reduced. Can be avoided.

When the printed board 4 is received by the conveyor 42 and the conveyor 43 by the lowering of the suction block 51, the arrow N in FIG.
As shown by 11, the CPU 92 drives the first Z motor 32 to move down the clamper 38 and the second block 37 together with the first elevating plate 31 and the clamper 38 and the second block 3.
7 is separated from the lower surface of the mask plate 2 at high speed, and as shown by an arrow N12, the CPU 92
Then, the second Z motor 47 is driven to lower the suction block 51. Although the present embodiment employs the above-described configuration, the abutting unit may be configured to move the mask plate 2 up and down with respect to the printed board 4, the clamper 38, and the second block 37.

[0028]

According to the screen printing method of the present invention ,
Print base without discoloration of cream solder
It can be applied to a board .

[Brief description of the drawings]

FIG. 1 is a perspective view of a screen printing apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of a substrate positioning unit of the screen printing apparatus according to one embodiment of the present invention.

3A is a diagram illustrating the operation of a screen printing apparatus according to one embodiment of the present invention; FIG. 3B is a diagram illustrating the operation of a screen printing device according to one embodiment of the present invention; (D) is an operation explanatory diagram of the screen printing device in one embodiment of the present invention. (E) is an operational explanatory diagram of the screen printing device in one embodiment of the present invention.

FIG. 4 is a front view of a conventional screen printing apparatus.

5A is a diagram illustrating the operation of a conventional screen printing device. FIG. 5B is a diagram illustrating the operation of a conventional screen printing device. FIG. 5C is a diagram illustrating the operation of a conventional screen printing device.

FIG. 6 is an enlarged view of a printed circuit board after cream solder is applied by a conventional screen printing apparatus.

[Explanation of symbols]

 Reference Signs List 1 screen mask 2 mask plate 12 squeegee 37 second block 38 clamper 47 second Z motor 90 control unit

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41F 15/26 B41F 15/40 B41F 15/08

Claims (1)

(57) [Claims] 1. A print having a lower surface sucked by a suction block.
The substrate is brought into contact with the lower surface of the mask plate,
Print squeegee by sliding the squeegee
A cream solder screen that prints cream solder on the top of the board
A chromatography screen printing method, slide the squeegee in the mask plate and print
After screen printing on the upper surface of the substrate,
The lower surface of the seat is received by the lower receiving part and
Suction block with biased key plate against mask plate
Release the substrate from the mask plate by lowering
Screen printing of cream solder characterized by
Method.