JP3152482B2 - Solder forming method in electronic component mounting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder forming method and an electronic component mounting method in a technique for mounting an electronic component on a circuit board.

[0002]

2. Description of the Related Art TAB parts (Tape Automat)
ed Bonding) and QFP (Quad Flat)
In the case where a lead portion such as a package is mounted on a circuit board, the pitch between the lead portions is becoming narrower recently. Therefore, a solder forming method corresponding to this is required.

As an example of this solder forming method, a method of forming a solder portion using a screen mask 21 shown in FIGS. 7 and 8 is known. This screen mask 21
Has a plurality of openings 22 at positions corresponding to the leads of an electronic component (not shown). Each of the apertures 22 is
In some cases, a rectangle is provided with a quarter roundness at its four corners.

When a solder portion is formed by using the screen mask 21, the screen mask 21 is disposed on a conductor 26 provided on the circuit board 21, as shown in FIG. Then, the semi-solid cream solder 3 is placed on the upper surface of the screen mask 21, the plate-shaped squeegee 4 is moved along the upper surface, and printing is performed so that the cream solder 3 is filled in the opening 22. Thereafter, when the screen mask 21 is removed, a solder portion 27 is formed on the upper surface of the conductor portion 26.

[0005] Thereafter, the circuit board 25 is passed through a reflow furnace to heat and melt the solder portions 27 while the lead portions of the electronic components are in contact with the plurality of solder portions 27, and the conductor portions provided on the circuit board 25 are melted. 26, the lead of the electronic component is connected.

[0006] In addition to the above-described solder forming method, electroplating is performed by immersing a circuit board in a plating solution and applying a voltage between positive and negative electrodes to form a solder portion on a conductor provided on the circuit board. Laws have also been adopted.

[0007]

However, in order to reduce the pitch of each solder portion 27 in correspondence with the lead portion of an electronic component which tends to be narrowed, the opening portion of the rectangular screen mask 21 is required. It is necessary to reduce the width of each other. In order to reduce the width, the thickness of the screen mask 21 must be increased, and as the thickness increases, the contact surface between the inner wall 22a of the opening 22 and the solder increases. Then, after the formation of the solder portion 27, the screen mask 2 is formed.
When 1 is removed, a part of the solder adheres to the inner side wall 22a of the opening 22 and there is a problem that the so-called printing-out is deteriorated.

[0008] When a part of the solder adheres, the shape of the solder portion 27 is deformed and the total amount is reduced, which hinders the fusion and connection to the lead portion of the electronic component. There was a case. Further, if the screen mask 21 is continuously used with the solder adhered to the opening 22, the supply amount of the solder is reduced. Therefore, after the screen mask 21 is used, the solder is blown off and cleaning is performed. Needed. When performing this cleaning, the continuous work must be temporarily suspended, so that the mounting efficiency has been significantly reduced.

In view of the above problems, the opening 2
Although it is conceivable to increase the width of No. 2, there is a disadvantage that the supply of the solder becomes excessive and becomes uneconomical.

In the case of the electroplating method, the conductor 2
In addition, there is a problem that the thickness of the solder portion formed on the substrate No. 5 is not uniform and a connection failure is likely to occur. In addition, a device such as a plating tank or an electric facility is required, resulting in an increase in cost.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and in particular, to solve the above-mentioned problems with respect to mounting of an electronic component having a gold bump.

[0012]

According to the present invention, a semi-solid solder is filled in the opening using a screen mask in which an opening is formed at a position facing the conductor provided on the circuit board. In the method of forming a solder in an electronic component mounting by printing on a conductor portion and forming a solder portion on the upper surface of the conductor portion, the electronic component is an electronic component having a gold bump, and the gold bump of the conductor portion is connected. The printing is performed by using a screen mask in which a plurality of openings are formed for one gold bump at a position facing the portion, and the opening connects the conductor and the gold bump. It is characterized in that it is formed in a small shape with the amount of solder required to perform the process.

Preferably, the opening is substantially circular.

After the electronic component is mounted at a predetermined position on the circuit board, the solder portion is melted through a reflow furnace, and the conductor portion of the circuit board is connected to the gold bump of the electronic component.

[0015]

According to the present invention, a screen mask is placed on the upper surface of the conductor provided on the circuit board, and the opening is filled with semi-solid solder for printing. Then, when the screen mask is removed, a solder portion is formed on the conductor portion. At this time, when a plurality of bumps are provided for one gold bump, the screen mask is more easily removed than the conventional one.

That is, the conductor of the circuit board is opposed to the gold bump of the electronic component. If the pitch of the gold bump is narrow, the width of the opening of the screen mask must be narrow. In order to make this width smaller, the screen mask must be made thicker. However, when the mask becomes thicker, the contact surface between the inner wall of the opening and the solder becomes larger. In such a screen mask, the amount of solder adhering to the inner wall is increased by an amount corresponding to the increase in the contact surface of the solder when the screen mask is removed after use.

If a plurality of holes are provided for one gold bump as compared with the conventional case in which the shape of the hole is large, each hole can be reduced.
At this time, each opening can be made small as long as the amount of solder required to connect the conductor and the gold bump can be secured, and the screen mask can be made thin.

When the openings are filled with semi-solid solder and printed, the contact surface between the inner wall of each opening and the solder becomes small. The amount of solder adhering to the substrate is also small. As described above, when the printing plate removal property is good, the cleaning work for removing the residual solder in the opening portion becomes unnecessary.

Then, after mounting the electronic component at a predetermined position on the circuit board, the solder portion is melted through a reflow furnace.
The gold bump of the electronic component can be rationally connected to the conductor of the circuit board.

[0020]

Reference Examples and Examples of the Present Invention Hereinafter, reference examples and examples of the present invention will be described with reference to the drawings.

FIG. 1 is a process chart of a solder forming method according to a reference example. In this solder forming method, as shown in FIG. 1 (c), when connecting a lead portion 8 of an electronic component to a conductor portion 6 provided on a circuit board 5, an upper surface of the conductor portion 6 is formed using a screen mask 1. This is for forming the solder portion 7.

The screen mask 1 is made of metal, and an extremely thin metal mask having a thickness t of 5 μm to 100 μm is used. The screen mask 1 has a plurality of circular openings 2 as shown in FIG. Each of the apertures 2 is a set of four, and is composed of an aperture row 9 in the X direction and an aperture row 10 in the Y direction. Extends to.

When the solder portion 7 is formed by the screen mask 1, as shown in FIG.
(Cross-sectional view along line A), and the screen mask 1 is arranged on the conductor 6 provided on the circuit board 5. Then, a semi-solid cream solder 3 is placed on the upper surface of the screen mask 1, and a plate-shaped squeegee 4 is moved along the upper surface.
Printing is performed so as to fill the opening 2 with the cream solder 3 as shown in FIG. Thereafter, when the screen mask 1 is removed, a solder portion 7 is formed on the conductor portion 6.

At this time, the one provided with the aperture rows 9 and 10 composed of the circular apertures 2 has a plate mask of the screen mask 1 as compared with a case where one aperture is rectangular or elliptical. The omission is good. That is, when a plurality of circular openings 2 are provided as in this example, each opening 2 has a smaller shape than the conventional case in which the shape of the opening is large. . At this time, each of the openings 2 can be reduced to the limit of the amount of solder required to connect the conductor 6 and the lead 8 without considering the width as in the case of a rectangle. For this reason, since the screen mask 1 can be made as thin as possible, the contact surface between the inner wall 2a of each opening 2 and the solder 3 becomes smaller, so that when the screen mask 1 is removed, it adheres to the inner wall 2a. The amount of solder 3 to be applied is also small. Accordingly, when the screen mask 1 is removed, the plate removal property is improved, so that a cleaning operation for removing the residual solder 3 in the opening 2 is unnecessary, and a continuous operation of the solder forming process can be performed.

The solder portions 7 formed on the conductor portions 6 in this manner are arranged in a straight line corresponding to the lead portions 8 of the electronic components, and the electronic components can be mounted on the circuit board 5.

Subsequently, in the case of mounting electronic parts, FIG.
As shown in (c), the lead portion 8 of the electronic component is connected to the solder portion 7.
Contact. Then, the circuit board 5 is passed through a reflow furnace (not shown) to melt the solder portion 7 on the conductor portion 6 and then cool and harden the lead portion 8 of the electronic component to the conductor portion 6
Is connected.

Each row of the solder portions 7 is narrowed according to the width between the lead portions 8 of the electronic component by setting the width w of each of the aperture rows 9 and 10 of the screen mask 1 to a narrow pitch. Pitching becomes possible. Further, since the solder portion 7 is thinly coated on the conductor portion 6, the amount of solder used is also greatly reduced.

Next, an embodiment of the present invention will be described.
The solder forming method according to this embodiment uses a flip chip 1 on a conductor 14 provided on a circuit board 13 shown in FIG.
The solder portions 15 for connecting the gold bumps 17 are formed.

In this embodiment, a screen mask 1b shown in FIG. 4 is used. This screen mask 1
“b” is made of the same material as the screen mask 1 of the above reference example, and two of them form a pair of apertures 2 in a substantially rectangular shape corresponding to the gold bumps 17 of the flip chip 16.

The case where a solder portion is formed using the screen mask 1b will be described. First, BB in FIG.
As shown in FIG. 5A, which is a cross-sectional view taken along the line, the screen mask 1b is arranged on the conductor portion 14 provided on the circuit board 13. Then, the semi-solid cream solder 3 is placed on the upper surface of the screen mask 1b, the plate-shaped squeegee 4 is moved along the upper surface, and printing is performed so that the cream solder 3 is filled in the opening 2. Thereafter, when the screen mask 1b is removed, as shown in FIG.
A set of two solder portions 15 is formed on the upper portion.

Also in this example, since each opening 2 is circular and the screen mask 1b can be made thinner, the screen mask 1b is easily removed from the plate and the inner wall 2a of the opening 2 is good.
Is prevented from being attached to the solder.

Then, the flip chip 1 is mounted on the circuit board 13.
6 is attached, as shown in FIG.
A convex gold bump 17 is brought into contact between the solder portions 15 on the substrate 4. In this state, the circuit board 13 is passed through a reflow furnace to melt the solder portions 15 on the conductor portion 14.
When cooled and cured, the gold bumps 17 of the flip chip 16 are connected to the conductor portions 14. Since these solder portions 15 can also be made narrower in the width of each row, the flip chip 16
Of the gold bumps 17 can be narrowed.

FIG. 3 shows a screen mask 1a in which the openings 2 are formed in the gold bumps 17 in one-to-one correspondence.

FIG. 6 shows a screen mask 1c according to another reference example, in which a plurality of circular openings 2 are formed alternately in the longitudinal direction. These apertures 2 are a set of two rows, one row 18 in the X direction and one row Y in the Y direction.
9 and extend radially in four directions corresponding to the leads of the electronic component (not shown). The rows of apertures 18, 19
Each pitch w corresponds to the pitch width of the lead portion of the electronic component. When this screen mask 1c is used, a staggered solder portion is formed on the conductor portion of the circuit board.

Subsequently, when mounting the electronic parts, the solder parts are melted through a reflow furnace (not shown).
The gaps between the respective solder portions are filled to form a substantially linear shape in which a plurality of solder portions are connected. Thereafter, when the leads of the electronic component are brought into contact with these solder rows and the solder is melted and cooled and hardened, the leads of the electronic component are connected to the conductors. This embodiment has an advantage that the amount of solder can be reduced because the amount of solder can be reduced by the gap between the solder portions.

Although the apertures 2 are circular in the above-mentioned reference examples and embodiments, they may be substantially circular.

[0037]

As described above, according to the present invention, a solder portion is formed on a conductor provided on a circuit board by using a screen mask in which a plurality of openings are formed for one gold bump. In addition, since the opening is formed in a small shape that limits the amount of solder required to connect the conductor and the gold bump, the connection between the gold bump of the electronic component and the conductor of the circuit board is made by soldering. Can be done reasonably,
The removal of the screen when removing the screen mask is improved,
Adhesion of solder to the inner wall of the opening can be greatly reduced. This eliminates the need for conventional work such as cleaning the solder adhering to the opening, and significantly improves the mounting efficiency of electronic components.

Further, since a solder portion to which a required amount of solder is supplied is formed on the conductor portion of the circuit board, when the electronic component is connected to the gold bump by fusion, a connection failure due to an insufficient amount of solder. Problem can be prevented.

Further, since the screen mask can be made thinner, there is an effect that the amount of solder used can be reduced.

[Brief description of the drawings]

FIG. 1 is a process chart of a solder forming method in electronic component mounting according to a reference example.

FIG. 2 is a perspective view of a screen mask used in the solder forming method.

FIG. 3 is a perspective view of a screen mask used in a solder forming method of another reference example.

FIG. 4 is a perspective view of another screen mask used in the solder forming method according to the embodiment of the present invention.

FIG. 5 is a process chart of a solder forming method in electronic component mounting of the same embodiment.

FIG. 6 is a perspective view showing still another reference example of the screen mask.

FIG. 7 is a perspective view of a screen mask used in a conventional solder forming method.

FIG. 8 is a process chart of a conventional solder forming method in electronic component mounting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screen mask 2 Opening part 3 Solder 5 Circuit board 6 Conductor part 7 Solder part

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-158585 (JP, A) JP-A-3-131858 (JP, A) JP-A-59-181694 (JP, A) JP-A-55-158694 55598 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/34 505 H01L 21/60 311

Claims (3)

(57) [Claims] 1. A semi-solid solder is filled in the opening and printed on the conductor using a screen mask having an opening formed in a portion facing the conductor provided on the circuit board. In a method for forming a solder in an electronic component mounting in which a solder portion is formed on an upper surface of a conductor portion , the electronic component includes a gold bump.
An electronic component to which a gold bump of the conductor is connected
At a position facing each other, one gold bump
The printing is performed using a screen mask having an opening.
And the opening portion connects the conductor portion and the gold bump.
A small shape that limits the amount of solder required for connection
Solder forming method of an electronic component mounting which is characterized in that which has been formed. 2. The method according to claim 1, wherein the opening is substantially circular . 3. The electronic component mounting according to claim 1 or 2.
After mounting the electronic component at a predetermined position on the circuit board on which the solder is formed by the solder forming method, the solder portion is melted through a reflow furnace, and the conductor of the circuit board and the metal of the electronic component are melted.
Electronic component mounting method characterized by connecting to bumps
Law.