JP3303603B2 - Screen printing method of cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to the cream solder of the scan screen printing method for printing a cream solder for soldering the electronic components on a substrate.

[0002]

2. Description of the Related Art Generally, cream solder for soldering electronic components is applied to a substrate by a screen printing apparatus. FIG. 4 is a schematic side view of a conventional cream solder screen printing apparatus. Reference numeral 1 denotes a substrate on which a screen mask 2 is disposed. 3 is a mask holder. Reference numeral 4 denotes a squeegee, which is held by a squeegee holder 5. The squeegee 4 is formed of an elastic material such as a resin, and extends downward from the squeegee holder 5 so as to be freely bent following the deflection of the substrate 1. 6 is a cream solder.

Therefore, when the squeegee 4 is slid on the screen mask 2, the cream solder 6 is printed on the substrate 1 through the pattern holes (not shown) formed in the screen mask 2. The printed substrate 1 is transported to the next step by a conveyor (not shown).

[0004]

As shown in FIG. 4, the substrate 1 has a flexure, and the squeegee 4 slides on the screen mask 2 while bending while following the flexure.
The screen mask 2 is formed of a material having sufficient flexibility such as a thin stainless plate. FIG. 4
Here, the deflection of the substrate 1 is exaggerated.

In FIG. 4, the attack angle (the angle at which the squeegee 4 contacts the screen mask 2) θ1 is small on a high position of the substrate 1, and the attack angle θ2 is large on a low position of the substrate 1. As the attack angle varies, the contact strength of the squeegee 4 to the screen mask 2 also varies. When the ground strength fluctuates in this manner, the cream solder 6 on the screen mask 2 oozes out to the bottom surface of the screen mask 2 through the pattern holes, and the oozed cream solder 6 is transferred to the upper surface of the substrate 1 and
There is a problem that the print quality is easily contaminated and the print quality tends to fluctuate.

When the squeegee 4 is replaced, the squeegee 4 is initialized. The initial setting is to adjust the pressing amount (falling amount) of the squeegee 4 to adjust the contact strength and the attack angle with respect to the screen mask 2, but in the conventional screen printing apparatus, the Young's modulus of the squeegee 4 is not uniform. Therefore, the initial setting work requires a great deal of time and labor.

Accordingly, the present invention can maintain the ground strength and attack angle of the squeegee with respect to the screen mask at a predetermined size in accordance with the deflection of the substrate, and can easily perform the initial setting of the squeegee . and to provide a scan click <br/> screen printing method.

[0008]

The present invention for this purpose is based on
Slide the key on the screen mask by the driving means.
To print cream solder on the board
A method of printing solder, comprising:
Apply downward fluid pressure to the squeegee and apply a constant force to the squeegee.
Press against the screen mask and advance the squeegee
Squeegee holder that extends to the lower part on the back side in the direction
Skiing while maintaining a constant squeegee attack angle
The slide was made to slide on the screen mask .

[0009]

[0010]

According to the above arrangement, regardless of the deflection of the substrate,
The squeegee can be grounded to the screen mask with a predetermined grounding strength and attack angle, so that cream solder of stable quality can be printed.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 is a side view of a cream solder screen printing apparatus according to one embodiment of the present invention, FIG. 2 is a side view of the squeegee, and FIG. 3 is a cross-sectional view of the print head.

In FIG. 1, reference numeral 11 denotes a substrate on which a cream solder 12 is applied, which is held by a substrate holder 13. Reference numeral 14 denotes the substrate 11 in the X and Y directions, and θ (horizontal rotation).
It is a movable table that moves in the direction.

The screen mask 1 is provided on the upper surface of the substrate 11.
5 are arranged. A pair of left and right squeegees 16a and 16b are provided on the screen mask 15, and the cream solder 12 is inserted between the squeegee 16a and the squeegee 16b. A horizontal holder 17 is provided above the screen mask 11, and two print heads 30a and 30b are provided on the holder 17.

A cream solder replenisher 21 is provided between the print heads 30a and 30b. This replenisher 21
In response to a command from the discharge control unit 23, the cream solder 12 is discharged from the nozzle 22 and supplied onto the screen mask 15. A nut 24 is provided on the side of the holder 17. A feed screw 25 is screwed to the nut 24 in a horizontal posture. When the motor 26 is driven forward and backward to rotate the feed screw 25 forward and backward, the nut 24 and the holder 17 integrated with the nut 24 slide reciprocally in the lateral direction, whereby the squeegee 1
6a and 16b reciprocate on the screen mask 15. A control unit 27 controls the entire apparatus.

In FIG. 2, the squeegee 16a is held by a squeegee holder 18. The lower end of the squeegee holder 18 extends to a lower portion on the back side in the traveling direction (rightward) of the squeegee 16a. By supporting the entire rear surface of the squeegee 16a with the squeegee holder 18, the squeegee 16a made of an elastic material is prevented from bending, and the squeegee 16a always keeps a constant attack angle θ. 15a is a screen mask 15
It is a pattern hole formed in the hole. Note that the other squeegee 1
6b is also held by the squeegee holder 18 by the same structure.

Next, the structure of the print head 30a will be described with reference to FIG. The other print head 30b has the same structure. The print head 30a holds the squeegee 16a vertically movably by a fluid pressure applying means including an air cylinder described below. 31 is a cylinder body,
A vertical shaft 32 penetrates therein. A piston 33 is connected to a lower end of the shaft 32. The rod 19a is connected to the lower surface of the piston 33,
The squeegee holder 18 is connected to the lower end of the rod 19a.

The upper end of the shaft 32 is a screw portion 32a, and a nut 35 is screwed. The upper part of the cylinder body 31 is connected to a valve 38 by a tube 36, and the lower part is connected to a valve 38 by a tube 37.
It is connected to the. The valve 38 is connected to a compressor 40 via a pressure control unit 39. The valve 38, the pressure control unit 39, and the compressor 40
8.

When air is supplied to the upper part of the cylinder body 31 through the tube 36, the piston 33 descends, and the squeegee 16a is pressed against the upper surface of the screen mask 15. The lower limit of the squeegee 16a is defined by the landing of the nut 35 on the upper surface of the cylinder body 31. In this embodiment, when the squeegee 16a is grounded on the screen mask 15, the lower end surface of the nut (stopper) 35 and the upper surface of the cylinder body 31 (reference) so that the squeegee 16a can move up and down following the deflection of the substrate 11. The position of the nut 35 is adjusted so that a gap G is formed on the (surface).

When air is supplied to the lower portion of the cylinder body 31 through the tube 37, the piston 33 rises, and the squeegee 16a also rises and separates from the screen mask 15.
According to such a fluid pressure applying means, the squeegee 16a can always be pressed against the upper surface of the screen mask 15 with a predetermined strength by the air pressure regardless of the deflection of the substrate 11. In this embodiment, an air cylinder is used, but a fluid pressure other than air may be applied to the squeegee 16a.

This cream solder screen printing apparatus is constructed as described above, and its operation will be described below. In FIG. 1, with the left squeegee 16a grounded on the screen mask 15 and the right squeegee 16b retracted upward, the motor 26 is driven to slide the squeegee 16a to the right to The cream solder 12 is printed on the substrate 11 through the pattern holes 15a of the mask 15. When printing is completed, the substrate 11 is sent out to the next step by a conveyor (not shown). Next, a new substrate 11 is positioned on the substrate holder 13. Next, the left squeegee 16a is retreated upward, and the right squeegee 16b
Is grounded on the screen mask 15, the motor 26 is rotated in the reverse direction, the squeegee 16b is slid to the left, and the cream solder 12 is printed on the substrate 11.

By repeating the above operation, the cream solder 12 is printed on the substrate 11 one after another. As described with reference to FIG. 3, the squeegees 16a, 16b
Is pressed against the screen mask 15 by the air pressure supplied to the cylinder body 31, so that the squeegees 16a,
6b is always pressed against the screen mask 15 with a constant force. Further, as described with reference to FIG. 2, the squeegees 16a and 16b are supported on the entire back surface thereof by the squeegee holder 18 and cannot be bent. Therefore, even if the substrate 11 is bent, the attack angle θ can be reduced. Can be kept constant. From the above, the squeegees 16a, 1
6b, the contact strength and the attack angle θ are kept constant, so that printing with stable quality can be performed.

[0022]

As described above, according to the present invention, the squeegee is made to slide on the screen mask at a predetermined ground strength and an attack angle regardless of the deflection of the substrate.
Therefore, it is possible to print cream solder with stable quality.

[Brief description of the drawings]

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

FIG. 2 is a side view of a squeegee of the screen printing apparatus for cream solder according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a print head of the screen printing apparatus for cream solder according to one embodiment of the present invention.

FIG. 4 is a schematic side view of a conventional cream solder screen printing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Cream solder 15 Screen mask 16a, 16b Squeegee 18 Squeegee holder 25 Feed screw 26 Motor 30a, 30b Print head 31 Cylinder main body 33 Piston

Claims (1)

(57) [Claims] 1. A cream solder printing method in which a squeegee is slid on a screen mask by driving means to print cream solder on a substrate, wherein a fluid pressure applying means applies a downward fluid pressure to the squeegee. And press the squeegee against the screen mask with a constant force, and
Extends to the lower part on the back side in the direction of travel of the squeegee
The squeegee holder keeps the squeegee attack angle constant.
A screen printing method for cream solder, wherein a squeegee is slid on a screen mask.