JP3150073B2 - 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 method for printing cream solder, and more particularly to a method for printing cream solder for printing on a printed circuit board having a fine pattern.

[0002]

2. Description of the Related Art Conventional cream solder printing methods generally include a contact method in which a printed circuit board and a metal mask are brought into close contact with each other for printing, and an off-contact method in which a gap is provided between the printed circuit board and the metal mask for printing. There is.

FIGS. 3A and 3B are schematic cross-sectional views showing steps of a conventional cream solder printing method. FIG. 3A shows a state immediately after printing, and FIG. 3B shows a state in which the printed board is lowered. In the figure, reference numeral 31 is a squeegee, 32 is a metal mask frame, 33 is cream solder, 34 is a metal mask, 35
Is an opening of a metal mask, 37 is a table for supporting a printed board, 38 is a pad provided on the printed board,
39 is a printed circuit board.

In the contact method, as shown in FIG. 3A, an opening 35 of a metal mask 34 and a pad 38 provided on a printed board 39 fixed on a table 37 are provided.
The squeegee 31 is moved in a state where the squeegees 31 are brought into close contact with each other, and the cream solder 33 is printed in the openings 35 and placed on the printed circuit board 39. Thereafter, as shown in FIG. 37 is lowered to the printed circuit board 39
This is a method of printing the cream solder 33 on the pad 38 of the printed circuit board 39 by pulling the cream solder 33 placed away from the metal mask 34 through the opening 35.

[0005] In the contact method, the cream solder 3 is placed in a state where the metal mask 34 and the printed board 39 are in close contact with each other.
No. 3 is imprinted and separated vertically, so that a good printed shape can be obtained, which is currently the mainstream of cream solder printing.
Especially in fine pattern printing, the printed circuit board 39
Is controlled at a very low speed to facilitate the flow of the cream solder 33 on the wall surface of the opening 35 of the metal mask 34.
Since the pressure between the metal mask 9 and the metal mask 34 is low, the metal mask 34 is prevented from being bent, so that the cream solder can be stably removed.

[0006] The off-contact method is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-313895 published on December 21, 1988, in which a cream is provided with a mechanism for keeping the plate separation angle between a metal mask and a printed circuit board constant. A solder printing machine is shown. FIG. 4 is a schematic cross-sectional view of a cream solder printing machine described in Document 1, in which reference numeral 41 is a squeegee, 42 is a frame, 44 is a metal mask, 45 is a push-up mechanism, 46 is a frame guide, and 47 is a stopper. , 49 are printed circuit boards.

As shown in FIG. 4, in the conventional off-contact type cream solder printing method, the squeegee 41 is moved so that the angle between the metal mask 44 and the printed circuit board 49 becomes constant in accordance with the movement of the squeegee 41. In this method, the frame 42 on the rear side in the direction is raised by the push-up mechanism 45.

[0008]

In the conventional method of printing cream solder by the contact method, the metal mask 34 is bent by the adhesive force of the cream solder 33 even if the table 37 is moved down at a very low speed, so that the center portion and the end of the printing area are printed. 3B, the angle of the plate separation is not vertical as shown in FIG. 3 (b). As a result, the problem that the paste removal property of the cream solder deteriorates and the printing amount varies. there were. Also, when the size of the metal mask is enlarged to accommodate large printed boards such as multi-cavity printed boards, or when the thickness of the metal mask is reduced due to the miniaturization of the printed pattern, the rigidity of the metal mask decreases. There has been a problem that the amount of deflection is large.

In the conventional method of printing cream solder by the off-contact method, since the printing is performed by bending the metal mask, the separation speed of the plate cannot be controlled, and even if the bending angle of the metal mask can be fixed, the conventional method is not used. However, there is a problem that the printout is poorer than that of the contact type printing method, and the printing amount varies.

An object of the present invention is to provide a cream solder printing method capable of transferring cream solder imprinted into an opening of a metal mask to a printed board in a good shape.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for printing cream solder in which a printed board is brought into close contact with a lower surface of a metal mask having a fixed opening, and a squeegee is scanned over the upper surface of the metal mask. The cream solder is placed at a predetermined position on the upper surface of the printed circuit board through the section, the printed circuit board is lowered vertically, and the cream solder placed on the printed circuit board is pulled out from the opening to perform printing. In the method, the printed circuit board is lowered while the lower surface of the fixed metal mask is supported by a support surface of a mask support pin disposed below the metal mask.

In this solder printing method, the mask support
The pins are supported near the outside of the printed circuit board and
This is the position of the through hole provided in the lint substrate.

By lowering the table vertically by supporting the vicinity and the center of the pattern of the metal mask with the mask support pins from the lower surface, the metal mask is prevented from bending, the plate separation speed can be kept constant over the entire printing area, and printing can be performed. The quantity stabilizes.

[0014]

FIG. 1 shows a central portion of a metal mask .
It is a schematic cross-sectional view showing a step of the printing method of cream solder when not holding , (a) is a state immediately after printing,
(B) is a state where the printed board is lowered. In the figure, reference numeral 11 denotes a squeegee, 12 denotes a frame of a metal mask, 13 denotes cream solder, 14 denotes a metal mask, 15 denotes an opening of the metal mask, 16 denotes a mask support pin, 17 denotes a table for supporting a printed circuit board, and 18 denotes a print. Pads 19 provided on the substrate are printed circuit boards.

In the method for printing cream solder of the present invention,
Metal mask 1 arranged at the printing position as shown in FIG.
4 so that the support surface is in close contact with the lower surface of the mask support pin 4.
6 are provided. It is desirable that the supporting position is a position where the metal mask 14 is evenly supported on a plane in the vicinity of the outer edge of the area where the opening 15 is formed.

As shown in FIG. 1A, the mask support pins 16 and a printed circuit board 19 fixed to a table 17 are placed on the lower surface of the metal mask 14, and the opening 1 of the metal mask 14 is formed.
5 and the pad 18 provided on the printed board 19 are aligned and brought into close contact with each other, the squeegee 11 is moved, the cream solder 13 is printed on the opening 15 and placed on the printed board 19, and thereafter, As shown in FIG. 1B, with the mask support pins 16 in contact with the metal mask 14, the table 17 is lowered to separate the printed circuit board 19 from the metal mask 14 so that the cream solder 13 placed thereon is opened. By pulling out the solder paste from 15, the printing of the cream solder 13 on the pads 18 of the printed circuit board 19 is completed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for printing a cream solder when the central portion of a metal mask is not supported will be described with reference to FIG. This
As shown in FIG. 1 (a), the cream solder printing method first includes a pad 18 of a printed board 19 sucked and fixed on a table 17 and a mask supporting pin 16 provided close to the outside of the printed board. The squeegee 11 is moved on the metal mask 14 in a state where the squeegee 11 is in close contact with the back surface of the metal mask 14 attached to the frame 12, and the cream solder 13 is supplied into the opening 15 provided in the metal mask 14. . Next, as shown in FIG. 1B, while the mask support pins 16 are in close contact with the metal mask 14, the printed circuit board 19 is vertically moved down slowly by the table 17 to separate the printed circuit board 19 from the metal mask 14. By pulling out the placed cream solder 13 from the opening 15, printing of the cream solder 13 on the pad 18 is performed. The mask support pins 16 of this example are installed on the outer peripheral portion of the printed circuit board, and are effective for a small printed circuit board for performing fine pattern printing.

Implementation of the cream solder printing method of the present invention
An example will be described with reference to FIG. 2A and 2B are schematic cross-sectional views showing the steps of an embodiment of the method for printing cream solder of the present invention. FIG. 2A shows a state immediately after printing, and FIG. 2B shows a state in which the printed board is lowered. In the figure, reference numeral 21 denotes a squeegee, 22 denotes a metal mask frame, 23 denotes cream solder,
24 is a metal mask, 25 is an opening of the metal mask, 2
6 is a mask support pin, 27 is a table for supporting the printed board, 28 is a pad provided on the printed board, 29
Is a printed circuit board.

The method of printing cream solder according to the embodiment of the present invention is a method of printing on a multi-cavity printed circuit board having through holes for division. A plurality of mask support pins 26 are arranged in the outer peripheral portion and the central through hole of the printed circuit board 29, and the squeegee 21 is moved to move the cream solder 23 to the opening of the metal mask 24 as in the first embodiment. After being supplied to the metal mask 25, the table 27 and the printed circuit board 29 are moved down at a very low speed while keeping the mask support pins 26 in close contact with the metal mask 24. In this case, a hole through which the mask support pin passes may be provided on the printed circuit board side in accordance with the arrangement of the mask support pin.

[0020]

The effect of the present invention is that the printing amount of the solder paste is stabilized. The reason is that the metal mask is supported by the mask support pins when performing the plate separation operation after squeezing, so the deformation of the metal mask due to the adhesive force of the cream solder is eliminated, and the plate separation speed is uniform over the entire printing area Because it becomes.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing steps of a method for printing a cream solder when a central portion of a metal mask is not supported . (A) is a state immediately after printing. (B) is a state where the printed board is lowered.

FIG. 2 is a schematic cross-sectional view showing the steps of an embodiment of the cream solder printing method of the present invention. (A) is a state immediately after printing. (B) is a state where the printed circuit board is lowered.

FIG. 3 is a schematic cross-sectional view showing steps of a conventional cream solder printing method. (A) is a state immediately after printing. (B) is a state where the printed board is lowered.

FIG. 4 is a schematic sectional view of a cream solder printing machine described in Document 1.

[Explanation of symbols]

 11, 21, 31, 41 Squeegee 12, 22, 32, 42 Frame 13, 23, 33 Cream solder 14, 24, 34, 44 Metal mask 15, 25, 35 Opening 16, 26 Mask support pins 17, 27, 37 Tables 18, 28, 38 Pads 19, 29, 39, 49 Printed circuit board 45 Push-up mechanism 46 Frame guide 47 Stopper

Claims (1)

(57) [Claims] 1. A printed circuit board is brought into close contact with a lower surface of a metal mask having a fixed opening, and a squeegee is scanned on the upper surface of the metal mask to apply cream solder through the opening to a predetermined position on the upper surface of the printed circuit board. In the cream solder printing method of performing printing by pulling the cream solder placed on the printed circuit board vertically and pulling out the cream solder from the opening by lowering the printed circuit board vertically, The lower surface of the metal mask is placed near the outside of the printed circuit board below the metal mask and
A method of printing the cream solder, wherein the printed board is lowered while being supported by a support surface of a mask support pin provided at a position of a through hole provided in a center portion of the printed board.