JPH0692054A - Printing mask - Google Patents

Abstract

PURPOSE:To contrive to uniformize the printed amount of soldering paste by a method wherein the length of the side of a rectangular opening, which is provided in a printing mask for printing the soldering paste on each electrode pad of the wiring pattern of a printed board, is set in proportion to the moving direction (or angle) of a squeegee. CONSTITUTION:In the printing mask 10 concerned, a plurality of openings 10a and 10b, in which soldering paste is squeezed, are formed at positions corresponding to the respective electrode pads of the wiring pattern of a printed board. In the above-mentioned printing mask 10, the lengths of the shorter sides (b) and b' of the respective openings 10a and 10b are determined in proportion to the angles between the moving direction (a) of a squeegee and the longer sides of the openings. Concretely, the length (b) of the shorter side of the opening 10a, the longer side of which is normal to the moving direction, is made shorter than the length b' of the shorter side of the opening 10b, the longer side of which is parallel to the moving direction. The amount of soldering paste 4 printed by the opening 10a, through which the soldering paste 4 oozes much more, is made nearly equal to the amount of the soldering paste printed by the opening 10b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print mask for printing and supplying a solder paste on each electrode pad of a wiring pattern of a printed circuit board.

[0002]

2. Description of the Related Art For example, a large number of electronic components may be surface-mounted on a printed circuit board by soldering. In such a case, a reflow soldering method is generally used, which is capable of soldering a large number of electronic components collectively.

This reflow soldering is carried out in advance on each electrode pad of the wiring pattern of the printed circuit board.
Stroke-shaped solder (hereinafter referred to as "solder paste") is supplied, and the electronic component is placed on the printed circuit board so as to face the terminals of the electronic component and the electrode pads (solder paste). Place it.

When all the electronic components are mounted on the printed circuit board, the printed circuit board together with the electronic components is inserted into the reflow oven. With this, the solder paste
The strike melts and the electronic components are collectively surface-mounted on the printed circuit board.

In order to perform such reflow soldering with high accuracy, the solder paste is placed on each electrode pad of the wiring pattern, especially when the electrode pads are provided at a fine pitch. Need to be supplied to

As described above, there is a screen printing method as a method for accurately supplying the solder paste onto the printed circuit board. For example, as shown in FIG.
The print mask indicated by 1 in (a) is used. The print mask 1 is a screen-shaped thin plate, and as shown in FIG. 5, openings 1a corresponding to the respective wiring patterns of the printed circuit board.
Is provided.

At the time of printing, as shown in FIGS. 3A and 3B, first, the print mask 1 is overlaid on the upper surface of the printed circuit board 3 with a predetermined gap. Then, the print mask 1 is pressed downward by the squeegee 2 shown in the drawing and pressed against the printed circuit board 3, and the solder paste 4 supplied onto the mask 1 by the squeegee 2 is shown in the drawing. Move it in the direction indicated by the arrow (a). As a result, as shown in FIG. 4, the solder paste 4 is pushed into the openings 1a of the print mask 1.

Further, as shown in FIG.
When the printed wiring board 2 has passed, the print mask 1 is sequentially separated from the printed circuit board 3 from that portion, and the solder paste 4 pushed into the opening 1a is placed on the electrode pad 5 of the printed circuit board 3 shown in FIG. Is transcribed to.

[0009]

The amount and the printed state of the solder paste 4 printed on the electrode pad 5 depend on the moving direction of the squeegee 2 (hereinafter, simply referred to as "moving direction"). different. That is, as shown in FIG. 4, when the moving direction is the direction shown by the arrow (a), the moving direction of the squeegee 2 in the gap between the lower surface of the mask 1 and the upper surface of the printed circuit board 3 ) The solder paste 4 may wrap around to the front and the rear, causing bleeding. When the print mask 1 is separated from the upper surface of the printed circuit board 3 in this state, "drip" of the printed solder paste 4 occurs.

As shown in FIG. 5, the opening 1 of the conventional mask is shown.
If the areas of the electrode pads 5 of the wiring pattern on which the solder paste 4 is printed are the same, all of a have the same rectangular shape and the same size. For this reason, the width in which bleeding occurs is larger in the opening 1a whose longer side is orthogonal to the moving direction (a), so that the solder paste to be printed is correspondingly printed.
The amount of strike 4 increases. Therefore, the conventional print mask 1
However, the amount of the solder paste 4 supplied onto the electrode pad 5 may become non-uniform depending on the moving direction.

As a result, in a place where the amount of the solder paste 4 is large, the solder paste 4 "droops" and a defect such as a solder bridge occurs, and conversely, in a place where the amount of the solder paste 4 is small, a defect such as an unsolder occurs. was there. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a print mask in which the printing amount of solder paste is uniform.

[0012]

A first means of the present invention has a rectangular opening, and a squeegee is moved to push a paste-shaped solder material into the opening to make the solder material. In the print mask that supplies the print on the electrode pad,
The opening is characterized in that the length of the other side orthogonal to the one side is determined according to the angle formed by the one side and the moving direction of the squeegee.

The second means of the present invention has an elliptical opening, and the squeegee is moved to press the paste-shaped solder material into the opening, so that the solder material is placed on the electrode pad. In the printing mask for printing and supplying, the opening has a length of the other diameter orthogonal to the diameter depending on the angle formed by either the major diameter or the minor diameter of the opening and the moving direction of the squeegee. It is what

[0014]

According to such a structure, the sides and diameters of the openings are determined according to the moving direction of the squeegee, so that the amount of solder material printed by each opening can be made substantially equal. it can.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows a portion of the printing mask 10 of the present invention. This printing mask 10 is provided with a plurality of openings 10a ... 10b ... into which the solder paste 4 (solder material) is pushed, as in the conventional example.

The openings 10a, 10b of this printing mask 10
The lengths of the short sides b and b'of the above are determined by the angle formed by the long side and the moving direction of the squeegee 2 (hereinafter simply referred to as "moving direction"). Hereinafter, the print mask 10 corresponding to the case where the movement direction is the same as the conventional example (a) in FIG. 1 is shown in FIG.
Print mask 11 corresponding to the case where the moving direction is (b)
The print mask 12 corresponding to the case where the moving direction is (c) is shown in FIG.

The print masks 10, 11 and 12 shown in FIGS. 1 and 2A and 2B are all relieved in four directions.
The solder pads are placed on the electrode pads 5 facing the respective leads of the semiconductor electronic component (eg, QFP) formed by projecting the leads.
It is for printing the strike 4.

Each opening 1 of each print mask 10, 11, 12
0a and 10b are provided in a pattern corresponding to the electrode pad 5, and along the extending direction of the lead,
It is formed in a rectangular shape (rectangular shape) that is long in the outward direction.

First, the print mask 10 shown in FIG. 1 will be described. The length b of the short side of the opening 10a (hereinafter, referred to as "first opening 10a") provided in the print mask 10 whose long side is orthogonal to the moving direction (a) is the long side. ) Parallel to the opening 10b (hereinafter "second opening 10b")
It is formed smaller than the short side length b'of

That is, since the long side of the first opening 10a is orthogonal to the moving direction (a), the solder paste is different from the second opening 10b in which the side orthogonal to the moving direction (a) is the short side. -The amount of bleeding on strike 4 is large. Therefore, the length b of the short side of the first opening 10a is adjusted accordingly and the
The amount of the solder paste 4 printed by the opening 10a is substantially equal to the amount printed by the second opening 10b.

When printing is performed using the print mask 10, the squeegee 2 is moved in the direction indicated by the arrow (a) as shown by citing FIG. As a result, the solder paste 4 is pushed into the first and second openings 10a and 10b and printed on the electrode pads 5 of the printed circuit board 3.

In this case, the first and second openings 10a,
The bleeding still occurs on the side opposite to the moving direction (a) of 10b, but each short side b, b'so that the amount of solder paste to be printed is equal.
Since the length of the solder paste 4 is determined, the solder paste 4 is printed substantially uniformly on each electrode pad 5.

Next, as shown in FIG. 2A, when the moving direction (b) is inclined by about 45 degrees with respect to the moving direction (a) shown in FIG. 1, that is, the first opening 11a and the first opening 11a. The print mask 11 in the case where the long side of the second opening 11b forms 45 degrees with the moving direction (b) will be described.

Also in this case, the amount of the solder paste printed is the solder paste printed on each electrode pad 5 through the first and second openings 10a and 10b of the print mask 10 shown in FIG. The lengths b and b'of the short sides of the first and second openings 11a and 11b are determined so as to be equal to the amount of 4.

The shapes of the first and second openings 11a and 11b will be described by taking the first opening 11a as an example. That is, the solder paste 4 pushed into the first opening 11a bleeds on both the long side and the short side. At this time, the length b of the short side is set so that the amount of the solder paste 4 printed by the first opening 11a becomes equal to the amount printed by the first opening 10 of the print mask 10 of FIG. To make a decision.

Further, in this print mask 11, the printing conditions of the second opening 11b are the same as those of the first opening 11a, so that the size and shape may be the same.

If such a print mask 11 is used,
Even if the squeegee 2 is moved in the direction indicated by (b), the solder paste 4 having substantially the same amount as that of the print mask 10 shown in FIG.
Can be printed uniformly.

Further, as shown in FIG. 2B, when the moving direction (C) of the squeegee 2 is inclined by about 90 degrees as compared with the state of FIG. 1, that is, the length of the first opening 12a. A description will be given of the print mask 12 in which the side is parallel to the moving direction (C) and the long side of the second opening 12b forms (opposes) 90 degrees with the moving direction (C).

Also in this case, the amount of the solder paste 4 to be printed is the same as that of the first and second printed masks 10 shown in FIG.
In order to equalize the amount of solder paste 4 printed on each electrode pad 5 by the openings 10a, 10b of the first and second openings 12a, 12b.
Determine b '.

First, the first opening 12a will be described. The solder paste 4 pushed into the first opening 12a bleeds to the short side. At this time, the length b of the short side is made longer than that in FIG. 2 so that the amount of the solder paste 4 printed by the first opening 12a is the same as that of the print masks 10 and 11 in FIGS. It is determined so as to be equal to the amount printed by the first openings 10a and 11a.

Next, the second opening 12b will be described. Solder paste pressed into the second opening 12b
The strike 4 blurs to the long side. At this time, the length b ′ of the short side is made shorter than that in FIG. 2 so that the amount of the solder paste 4 printed by the second opening 12b is the same as that of the print masks 10 and 11 in FIGS. It is determined so as to be equal to the amount printed by the two openings 10b and 11b. The first and second openings 12 of the print mask 12 shown in FIG.
The conditions of a and 12b are completely opposite to those in the case of FIG.

In this way, the print masks 10, 11,
12 The first openings 10a, 11a, 12a and the second
By determining the lengths b and b ′ of the short sides of the openings 10b, 11b, and 12b of each of the openings 10b, 11b, and 12b according to the angle formed by the long sides and the moving directions (a), (b), and (c), It is possible to always make the amount of the solder paste 4 which can be printed on each electrode pad 5 substantially equal by the print masks 10, 11, and 12.

Therefore, unlike the conventional printing mask, the printing amount of the solder paste does not fluctuate, so that it is possible to effectively prevent the occurrence of solder bridges or unsoldered solder, and to perform better surface mounting. You can next,
A second embodiment of the present invention will be described.

The print mask 10 'of this second embodiment is
It is provided with first and second elliptical openings 10'a and 10'b. The minor axis lengths b and b ′ of the first and second openings 10′a and 10′b are determined according to the angle formed by the major axis and the moving direction.

That is, when the squeegee is moved in the direction indicated by (a) in FIG. 3, the length b of the minor axis of the first opening 10'a whose major axis is orthogonal to the moving direction (a) is The major axis is formed smaller than the minor axis length b'of the second opening 10'b parallel to the moving direction (a).

That is, since the major axis of the first opening 10'a is orthogonal to the moving direction (a), the second opening 10'b whose side orthogonal to the moving direction (a) is the minor axis b '. The amount of bleeding of the solder paste 4 is larger than that of. For this reason,
The length b of the minor axis of the first opening 10'a is adjusted accordingly, and the amount of the solder paste 4 printed by the first opening 10'a is adjusted by the second opening 10'b. The amount printed was made approximately equal.

When printing is performed using this print mask 10 ', the squeegee 2 is moved in the direction shown by the arrow (a), as shown by citing FIG. As a result, the solder paste 4 has the first and second openings 10'a, 10 '.
It is pushed into b and printed substantially evenly on each electrode pad 5 of the printed circuit board 3.

The moving direction is as shown in FIG.
As shown in (b), in the cases of (b) and (c), the first and second openings 10'a and 10'b are the same as the short sides b and b'of the first embodiment. The lengths of the minor axes b and b'of

According to this structure, even when the solder material is supplied in an elliptical shape, the print amount of the solder paste does not vary, so that it is effective to generate a solder bridge or unsoldered solder. It is prevented, and better surface mounting can be performed. It should be noted that the present invention is not limited to the above-mentioned one embodiment, and can be variously modified without changing the gist of the invention. For example, in the first embodiment,
Although the four corners of the first and second openings 10a and 10b have a right angle, they may have an R shape in which a long side and a short side are connected by a curve.

In addition, in the first and second embodiments, the long side or the long diameter is the moving direction of the squeegee (a), (b),
Although the length of the short side or the short diameter is determined according to the angle formed with (C), the length is not limited to this. On the contrary, the short side or short diameter is the direction of movement of the squeegee (a),
The length of the long side or the long diameter may be determined according to the angle formed by (b) and (c).

[0042]

As described above, the print mask of the present invention firstly has a rectangular opening, and the squeegee is moved to press the paste-shaped solder material into the opening. In the print mask for printing and supplying this solder material on the electrode pad, the length of the other side of the opening, which is orthogonal to the one side, is determined according to the angle formed by the one side and the moving direction of the squeegee. Is.

Secondly, a printing mask having an elliptical opening and moving the squeegee to press the paste-like solder material into the opening to print the solder material on the electrode pad. In the above-mentioned opening, the length of the other diameter orthogonal to the diameter is determined according to the angle formed by either the major axis or the minor axis of the opening and the moving direction of the squeegee.

According to this structure, the printing amount of the solder paste supplied on each electrode pad can be made substantially uniform. Therefore, there is an effect that it is possible to effectively prevent the occurrence of a solder bridge, unsoldered solder, or the like as in the conventional print mask.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

2A and 2B are plan views of the same.

FIG. 3 is a plan view showing a second embodiment.

FIG. 4A is a perspective view showing screen printing, and FIG.
Is also a side view.

FIG. 5 is an enlarged side sectional view showing a printing process.

FIG. 6 is a plan view showing a conventional example.

[Explanation of symbols]

4 ... Solder paste (solder material), 5 ... Electrode pad, 1
0 (11, 12) ... Printing mask, 10a (11a, 12)
a) ... First opening (opening), 10b (11b, 12b)
… Second opening (opening).

Claims (2)

[Claims] 1. A printing mask having a rectangular opening, wherein a squeegee is moved to press a paste-like solder material into the opening to print and supply the solder material onto an electrode pad. The printing mask, wherein the length of the opening is determined according to the angle between one side of the opening and the moving direction of the squeegee, and the length of the other side orthogonal to the one side. 2. A printing mask having an elliptical opening, wherein a squeegee is moved to press a paste-shaped solder material into the opening to print the solder material on an electrode pad. A printing mask, wherein the opening has a length of the other diameter orthogonal to the diameter depending on the angle formed by either the major diameter or the minor diameter of the opening and the moving direction of the squeegee.