JP2001358448A - Solder paste applying mask and method for mounting electronic component using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder paste applying mask which can apply solder paste so that while a solder ball is prevented from being formed, the fixing strength between an electronic component and a substrate is increased when the electronic component having a flank electrode formed is mounted on the substrate by reflow soldering. SOLUTION: This solder paste coating mask 17 is used to previously apply the solder paste to pads 16 formed on the substrate B when the electronic component 10 having the flank electrode 12 is mounted on the surface of the pads 16 by reflow soldering. The mask 17 has openings 18 formed corresponding to the nearly rectangular pads 16; and each opening 18 of the mask 17 has a part 18c so formed that the solder paste is applied at a nearly center part of at least the area of the pad 16 where the electronic component 10 is mounted and the part 18c is smaller than the width of the pad 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask for applying a solder paste, which is used when an electronic component is surface-mounted on a conductive mounting portion formed on a substrate by reflow soldering, and an electronic component using the mask. Regarding implementation method.

[0002]

2. Description of the Related Art Conventionally, when mounting a surface mount type electronic component on a substrate, a reflow soldering technique is often used. FIG. 5 is a perspective view showing an example of a surface-mounted electronic component, and FIG. 6 is a bottom view of the electronic component shown in FIG. According to FIG. 1, the electronic component 10 is formed in a substantially rectangular parallelepiped shape, and an upper surface electrode 11, a side surface electrode 12, and a lower surface electrode 13 are continuously formed on an upper surface 10a, a side surface 10b, and a lower surface 10c, respectively. ing. In addition, the side surface electrode 12 is formed with a concave portion 14 cut out in a substantially cylindrical shape.

In order to mount the electronic component 10 on a substrate, as shown in FIG. 7, a wiring pattern P is formed on a substrate B made of, for example, glass epoxy by, for example, a known photolithography method. P
Is applied in advance to the pad 16 formed at one end of the solder paste. Then, after mounting the electronic component 10 thereon, soldering is performed by reflow soldering in a reflow furnace.

More specifically, the pad 1 of the wiring pattern P
When a solder paste is applied in advance on 6, for example, a solder paste application mask (hereinafter simply referred to as “mask”) 31 made of stainless steel is used. The mask 31 has a plurality of openings 32 formed in accordance with the pads 16 on which the electronic components 10 are mounted. The mask 31 is set on the substrate B (see FIG. 7), and the solder paste supplied to the opening 32 of the mask 31 is pressed with a squeegee or the like, so that the solder paste is applied onto the pads 16.

In this case, if the pads 16 are formed in a substantially rectangular shape, for example, as shown in FIG. 8 corresponding to the shape of the lower electrode 13 of the electronic component 10, the mask 3
As shown in FIG. 9, one opening 32 is formed in a substantially long rectangular shape having substantially the same size and shape as the pad 16.

Then, the electronic component 10 is mounted on the applied solder paste. At this time, the electronic component 10
It is mounted on the pad 16 so as to cover about 2/3 of the pad 16. The electronic component 10 is transported to a reflow furnace in a state of being temporarily joined on the substrate B due to the viscosity of the solder paste, and reflow soldering is performed in the reflow furnace to form a solder fillet F as shown in FIG. And soldered to the substrate B.

[0007]

However, in the mounting process of the electronic component 10, when the electronic component 10 is mounted on the pad 16, the solder paste is used.
In some cases, the electronic component 10 is crushed by its own weight and overflows to the side of the electronic component 10. When reflow soldering is performed in a reflow furnace, the overflowing solder paste may be melted to generate a so-called solder ball.

When a solder ball is generated, the adjacent pads 16 may be short-circuited to cause a malfunction of the circuit. In particular, in recent boards, the density of mounted components has been increased, and the pitch between the pads 16 may be narrow. Therefore, it is desired to suppress the generation of the solder balls.

Therefore, in order to prevent the generation of solder balls, it is conceivable to apply a solder paste on the pads 16 using a mask 37 having a so-called home base-shaped opening 36 as shown in FIG. That is, the opening 36 has a portion 36 a corresponding to a region other than the region where the electronic component 10 is mounted in the pad 16 and a portion formed along the side electrode 12 having the concave portion 14 formed in a semicircular cross section. 36b.

According to the mask 37 having the opening 36, in the area of the pad 16 other than the area where the electronic component 10 is mounted, as shown in FIG. Can be formed.
However, on the other hand, the solder paste is hardly applied to the lower surface electrode 13 of the electronic component 10. In addition, when the electronic component 10 is mounted on the pad 16, a part of the solder paste is guided to the recess 14, so that the solder on the lower electrode 13 is insufficient. Therefore, it has been difficult to say that the lower surface of the electronic component 10 has sufficient adhesion to the substrate B.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been conceived in view of the above circumstances, and when an electronic component having a side electrode formed thereon is mounted on a substrate by reflow soldering,
It is an object of the present invention to provide a solder paste application mask capable of applying a solder paste so as to prevent the occurrence of solder balls and to enhance the adhesion between an electronic component and a substrate.

In order to solve the above problems, the present invention employs the following technical means.

According to the solder paste application mask provided by the first aspect of the present invention, an electronic component having side electrodes is surface-mounted on a conductive mounting portion formed on a substrate by reflow soldering. A solder paste application mask used when the solder paste is applied to the conductive mounting portion in advance, and the mask has a plurality of openings formed corresponding to the substantially rectangular conductive mounting portion. The opening of the mask has a predetermined portion formed so that solder paste is applied at least in a substantially central portion of a region where the electronic component is mounted in the conductive mounting portion,
The predetermined portion is characterized in that it is formed to be shorter than the length of the conductive mounting portion in the short direction.

According to this configuration, when the electronic component is surface-mounted on the substrate by reflow soldering, the solder paste is previously applied using the solder paste application mask.
It is applied on a pad as a conductive mounting portion formed on the substrate. In this case, a solder paste is applied on the pad in a shape corresponding to the opening of the mask. Therefore, if the solder paste application mask has a predetermined portion formed so that the solder paste is applied at a substantially central portion of a region of the pad where the electronic component is mounted, the mask corresponds to the predetermined portion. A solder paste is applied to the central portion of the pad to be soldered.

Thereafter, when the electronic component is mounted on the solder paste, the solder paste applied to the central portion of the pad is crushed by its own weight. In this case, since the predetermined portion of the mask is smaller than the length of the pad in the short direction, the solder paste is applied to the portion of the pad where the solder paste is not applied,
The pad moves along the lateral direction of the pad, and spreads to approximate the overall shape of the substantially rectangular pad. Thus, the solder paste does not overflow from the side surface of the electronic component, and the generation of solder balls can be prevented. In addition, since the solder paste is applied to almost the center of the pad, the bonding area of the solder to the pad on the lower surface of the electronic component is increased as compared with the conventional case, and the adhesion between the electronic component and the board can be further improved. it can. Therefore, it is possible to prevent a short circuit between the pads and the like, to improve the adhesion, and to provide a highly reliable circuit board in which malfunction of the electronic component is suppressed.

According to a preferred embodiment of the present invention, the opening of the mask has a first portion corresponding to a region other than a region where the electronic component is mounted in the conductive mounting portion, and a first portion corresponding to the first portion. A second portion is formed along the side surface electrode that is continuous and has a concave portion having a substantially semicircular cross section, and a third portion that is continuous with the second portion and corresponds to a predetermined opening. More specifically, the first portion is formed in a substantially long rectangular shape, the second portion is formed in a substantially trapezoidal shape, and the third portion extends along the longitudinal direction of the conductive mounting portion and has a substantially long rectangular shape. Is formed.

According to this configuration, a solder fillet is formed in an appropriate amount along the side surface of the electronic component on a region other than the region where the electronic component is mounted. Further, for example, since the side electrode of the electronic component has the concave portion, the solder fillet can be formed also on the surface of the concave portion, and the adhesion of the electronic component to the substrate can be further improved.

Further, according to the preferred embodiment of the present invention, the periphery of the opening is formed to be a continuous curve or straight line. For example, if there is an angular portion on the periphery of the opening, a part of the solder particles in the solder paste may catch on the angular portion, and the solder paste may not be appropriately applied to the pad. When the solder paste is applied, the solder paste smoothly passes through the opening of the mask. Therefore, the filling of the pad with the solder paste can be improved.

According to the method for mounting an electronic component provided by the second aspect of the present invention, a step of applying a solder paste to a conductive mounting portion formed on a substrate; A method of mounting an electronic component, comprising the steps of mounting and connecting the electronic component mounted on the solder paste to the substrate by reflow soldering, wherein the step of applying the solder paste on the conductive mounting portion includes: The method is characterized in that a solder paste is applied to a substrate by using a solder paste application mask provided by one side surface.

According to the electronic component mounting method according to the second aspect of the present invention, by using the solder paste application mask provided by the first aspect of the present invention, the method for mounting an electronic component according to the first aspect of the present invention is performed. The same effect as that of the solder paste application mask can be obtained.

[0021] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. In addition,
In the following description, the drawings referred to in the section of the related art will be appropriately referred to.

The solder paste application mask, which is a feature of this embodiment, is used when a surface-mounted electronic component on which side electrodes are formed is mounted on a substrate by reflow soldering. Hereinafter, a mounting method of the electronic component to which the solder paste application mask is applied will be described step by step.

As a method of mounting the electronic component, a step of applying a solder paste in advance on a pad as a conductive mounting portion formed at one end of the wiring pattern on the substrate, and mounting the electronic component on the solder paste The process of
It is roughly divided into a step of connecting the electronic component mounted on the solder paste to the substrate by reflow soldering.

As shown in FIGS. 5 and 6, a plurality of side electrodes 12 are formed on the side surface 10b and the upper surface 10a and the lower surface 1 are used as electronic components handled by this mounting method.
A substantially rectangular parallelepiped surface-mounted electronic component 10 having an upper surface electrode 11 and a lower surface electrode 13 continuous with the side electrodes 12 is used at 0c. On the side surface 10b of the electronic component 10, a concave portion 14 extending in the vertical direction and cut out in a substantially semi-cylindrical shape is formed.
Are formed. As will be described later, by forming a solder fillet in the concave portion 14, the bonding between the pad 16 and the electronic component 10 can be improved.

As shown in FIG. 1, a flat board B made of, for example, glass epoxy is used as a board on which the electronic component 10 is mounted, and a wiring pattern P made of copper or the like is formed on the board B. Is formed. For forming the wiring pattern P, a known photolithography method is used. That is, a resist material is applied to the substrate B having a copper foil on the surface, and exposure and development are performed using an exposure mask on which a desired pattern is formed. Then, by removing unnecessary parts of the copper foil by etching,
Wiring pattern P including pad 16 as conductive mounting portion
Is formed.

The shape of the pad 16 is formed according to the shape of the lower electrode 13 formed on the lower surface 10c of the electronic component 10. For example, according to the electronic component 10 shown in FIG. 6, since the lower surface electrode 13 is formed in a substantially rectangular shape, the pad 16 is formed in a substantially rectangular shape almost corresponding to the shape. In detail, when the electronic component 10 is mounted on the pad 16, the size of the pad 16 is set such that a part 16 a of the pad 16 on the wiring pattern P side is partially exposed, as shown in FIG. . This is because a solder fillet is formed in a region 16 a that is partially exposed on the surface of the pad 16, and in order to further enhance the adhesion between the pad 16 and the electronic component 10, similarly to the concave portion 14 of the side electrode 12. is there.

Next, the pads 16 formed on the substrate B
A solder paste is applied on the upper surface in advance. In this step, FIG.
2, as shown in FIG. 2, a solder paste application mask having a plurality of openings 18 (hereinafter simply referred to as a "mask").
17 is used. That is, the mask 17 is
The solder paste is supplied while being positioned on the substrate, and the solder paste is supplied from above. Then, the solder paste is applied onto the pad 16 by pushing the solder paste into the opening 18 while moving the solder paste with a squeegee or the like, for example.

The mask 17 is formed on the pad 16 on the substrate B.
Are prepared for each substrate B according to the arrangement and shape of the substrate. As described above, for example, the electronic component 1
In the case of mounting 0, two pairs of pads 16 are formed on the substrate B corresponding to the lower surface electrodes 13 of the electronic component 10,
Two pairs of openings 18 are formed in the mask 17 corresponding to the pads 16. Then, as shown in FIG. 2, when the pad 16 of the wiring pattern P is formed in a substantially long rectangular shape, the opening 18 of the mask 17 is also formed in a shape corresponding to the shape of the pad 16.

The opening 18 will be described in more detail.
8 are the electronic components 1 of the pads 16 as shown in FIG.
0 corresponds to the area 16a other than the area in which the first part 18 is mounted, and the first part 18a is formed in a substantially rectangular shape.
a, a second portion 18b having a substantially trapezoidal shape and formed along the concave portion 14 having a substantially semicircular cross section.
b, and a third portion 18 c having a substantially rectangular shape and extending along the longitudinal direction of the pad 16.

The third portion 18c is formed so that the solder paste is applied substantially at the center of the region of the pad 16 where the electronic component 10 is mounted. Specifically, the third portion 18c has a length L in the short direction of the pad 16.
It is formed to be smaller.

When the solder paste is applied on the substrate B using the mask 17 as described above, an application pattern corresponding to the shape of the opening 18 of the mask 17 is formed on the pad 16. That is, the solder paste is applied to the pad 16 in a region corresponding to a part of the second portion 18b of the opening 18 and a region corresponding to the third portion 18c.

Next, the electronic component 10 is mounted on the solder paste. In this step, after the solder paste is applied on the pad 16 in the above-described step, the electronic component 10 moved by the suction collet or the like is mounted on the solder paste.

In this case, the solder paste on the pad 16 corresponding to the third portion 18c is crushed by the weight of the electronic component 10. Since the solder paste is applied to a substantially central portion of the pad 16, the solder paste moves along the short direction of the pad 16 to a region on the pad 16 where the solder paste is not applied, and the pad having a substantially rectangular shape is formed. It spreads to approximate the overall shape of the sixteen. for that reason,
The solder paste does not overflow from the side surface of the electronic component 10.

That is, the opening 18 of the mask 17 is formed so that the solder paste does not overflow from the side surface of the electronic component 10, in other words, so that the solder paste can be applied to almost only the center of the pad 16 in advance. Is formed. Therefore, by using this mask 17,
The generation of solder balls can be prevented.

The second portion 18 on the pad 16
b, the solder paste in the area corresponding to the electronic component 1
By mounting the “0”, it is guided to the concave portion 14 of the side surface electrode 12 to form a solder fillet in the concave portion 14.
Therefore, also in this case, the solder paste does not overflow from the side surface of the electronic component 10. Therefore, the cleaning step for removing the solder balls, which has been conventionally performed, can be omitted, and a short circuit between the pads 16 can be prevented.

In this case, the solder paste is applied to the pad 1
6, the solder bonding area to the pad 16 on the lower surface of the electronic component 10 is increased on the lower surface of the electronic component 10 as compared with the related art, so that the adhesion between the electronic component 10 and the substrate B can be further improved. .

Next, the electronic component 10 mounted on the solder paste is connected to the substrate B by reflow soldering. In this step, the board B is transferred to a reflow furnace with the electronic component 10 mounted thereon, and the electronic component 10 is soldered to the board B in the reflow furnace. Specifically, the solvent in the printed solder paste is dried by heating,
The electronic component 10 and the substrate B are melted by cooling and cooling the solder powder component.
Are connected.

In this case, a sufficient solder fillet F can be formed in the region 16a corresponding to the first portion 18a other than the region where the electronic component 10 is mounted, as shown in FIG. Therefore, the fixation of the electronic component 10 to the substrate B can be further improved. In addition, the fixability due to the formation of the solder fillet F can be visually confirmed, and the appearance inspection becomes easy. Through these steps, a substrate B on which the electronic component 10 is appropriately mounted is obtained.

FIG. 4 is a view showing a modification of the opening of the mask. According to the figure, the periphery of the opening 22 of the mask 21 is formed to be a continuous curve or straight line. For example, if there is an angular portion on the periphery of the opening 22, a part of the solder particles in the solder paste may catch on the angular portion and the solder paste may not be appropriately applied to the pad 16. Thereby, when the solder paste is applied, the solder does not stick to the angular portion. Therefore, the solder paste can smoothly pass through the opening 22 of the mask 21 and the filling of the pad 16 with the solder can be improved.

Of course, the scope of the present invention is not limited to the above embodiment. For example, mask 1
As long as the opening 18 has a third portion 18c,
It may be formed in any shape. Further, as the electronic component 10 applied to the mounting method using the mask, other electronic components having side electrodes can be applied. The method of applying the solder paste on the pad in advance is not limited to the above method. Further, the wiring pattern of the substrate is not limited to the above embodiment.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a mask for applying a solder paste and a substrate according to the present invention.

FIG. 2 is a plan view of a main part of the mask shown in FIG.

FIG. 3 is an enlarged view of the mask shown in FIG. 2;

FIG. 4 is a plan view of a main part of a mask according to a modified example.

FIG. 5 is a perspective view of an electronic component.

FIG. 6 is a bottom view of the electronic component.

FIG. 7 is a perspective view of a main part of a conventional mask and substrate.

FIG. 8 is a plan view of a main part of a pad.

FIG. 9 is a plan view of a main part of a conventional mask.

FIG. 10 is a perspective view of a main part of a substrate on which electronic components are mounted.

FIG. 11 is a plan view of a main part of another conventional mask.

[Explanation of symbols]

 Reference Signs List 10 electronic component 14 recess 16 pad 17 mask 18 opening B substrate

Claims (5)

[Claims] A conductive mounting portion formed on a substrate;
A solder paste application mask used when applying a solder paste to the conductive mounting portion in advance when an electronic component having side electrodes is surface-mounted by reflow soldering, wherein the mask has a substantially rectangular shape. A plurality of openings are formed corresponding to the conductive mounting portion, and the opening of the mask is formed by applying the solder paste at least in a substantially central portion of a region of the conductive mounting portion where the electronic component is mounted. A solder having a predetermined portion formed so as to be applied, wherein the predetermined portion is formed so as to be shorter than a length of the conductive mounting portion in a short direction. Paste application mask. 2. An opening of the mask includes a first portion corresponding to a region of the conductive mounting portion other than a region where the electronic component is mounted, and a continuous semi-circular cross-section to the first portion. A second portion formed along the side electrode having the concave portion; and a third portion continuous with the second portion and corresponding to the predetermined portion.
The mask for applying a solder paste according to claim 1, comprising: 3. The first portion is formed in a substantially elongated rectangular shape, the second portion is formed in a substantially trapezoidal shape, the third portion extends along a longitudinal direction of the conductive mounting portion, 3. The mask for applying a solder paste according to claim 2, wherein the mask is formed in a substantially rectangular shape. 4. The solder paste application mask according to claim 1, wherein the periphery of the opening of the mask is formed to be a continuous curve or straight line. 5. A step of applying a solder paste on a conductive mounting portion formed on a substrate; a step of mounting an electronic component on the solder paste; and a reflow soldering the electronic component mounted on the solder paste. 5. A method for mounting an electronic component, comprising: a step of connecting to a substrate by a ring, wherein the step of applying a solder paste on the conductive mounting portion comprises the step of applying a solder paste according to any one of claims 1 to 4. A method for mounting an electronic component, comprising applying the solder paste to the substrate using a mask.