JP2003211862A - Method for solder printing, metal screen, and squeegee - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for solder printing for general purpose for an after-attaching component on a printed board having a previous-attaching component. <P>SOLUTION: A metal screen 1 has an opening 2 for not interfering with a bare chip previously-attached, in addition to an SMT component opening 4 for soldering a lead or the like of an SMT component after-attached to a printed board 7, and the opening 2 masks the bare chip and the board 7 of its periphery by covering an expansible rubber-like thin film 3 by stretching the film 3. The squeegee 5 has a distal end 10 made of two rows of elastic members at a body 9 made of a rigid member, cuts 11 of a longitudinal direction are provided at an interval of several mm at the ends 10 of the squeegee 5, arranged in a blind-like state. Thus, even when the screen 2 has a raised protrusion, the squeegee can escape from the protrusion. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder printing method, a metal screen and a squeegee, and in particular, an SMT component (surface mount component) is soldered to a printed circuit board which has already been flip chip mounted such as an MCM (Multi Chip Module). The present invention relates to a method of screen-printing a solder paste for applying, and a metal screen and a squeegee used for such solder printing.

[0002]

2. Description of the Related Art Generally, in solder printing on a printed circuit board, a metal screen is positioned and placed on the board, a solder paste is supplied onto the metal screen, and the metal screen is rubbed with the tip of a squeegee. It is performed using an automatic solder printing machine that moves the squeegee from one side to the other side at a constant speed.

In solder printing for soldering a SMT component as a subsequent component to a printed circuit board on which a bare chip is already mounted as a preliminary component, an existing general-purpose solder printing automatic machine is used to improve productivity. It will be one of the important factors. However, conventionally, it is very difficult to perform solder printing on a printed circuit board where the bare chip is attached first and the printing surface is not flat.Therefore, use a metal screen with a bare chip mounting part for manual printing (manual work). I had no choice.

Therefore, for example, in Japanese Unexamined Patent Publication No. 7-290851, a squeegee is provided with a convex portion corresponding to a pre-mounted component of the metal screen already mounted on the substrate, and a notch is provided at a position corresponding to the convex portion. There is disclosed a method of printing solder in which, when solder is applied to a printed board, only the portion corresponding to the convex portion of the squeegee is elastically deformed so as to avoid the convex portion of the metal screen.

[0005]

[Patent Document 1] Japanese Patent Application Laid-Open No. 7-29085
In the solder printing method disclosed in No. 1, a squeegee dedicated to the product specifications of the printed circuit board must be provided so that the squeegee has a notch corresponding to the pre-mounted component already mounted on the printed circuit board. Therefore, there is a problem that the squeegee cannot be used for general purpose.

Further, with respect to variations in the mounting position and height of the component with respect to the board and the shape of the component itself,
There is also a problem that the convex portion provided on the metal screen must be sufficiently large and high so that the preliminarily attached component does not interfere with the metal screen.

[0007] One of the objects of the present invention is to be used for a metal screen and an existing automatic solder printing machine which can be brought into close contact with a printed board in a solder printing process for a post-mounted component even if a pre-mounted component is present. An object of the present invention is to provide a squeegee and a solder printing method using them.

[0008]

SUMMARY OF THE INVENTION The present invention screen prints solder (8 in FIG. 4) for further mounting a retrofit component onto a printed circuit board (7 in FIG. 1) that already has a pre-attached component. In the metal screen (1 in FIG. 1) used for the above, an opening (2 in FIG. 1), which is provided at a position corresponding to the preceding component and has a size through which the preceding component passes, and stretchability stretched so as to close the opening. And a thin film (3 in FIG. 1).

The squeegee (5 in FIG. 2) used for screen-printing solder (8 in FIG. 4) on the printed circuit board (7 in FIG. 1) of the present invention has a large number of cuts (10 in FIG. 2) at the tip (10 in FIG. 2). Figure 2
According to 11), it is characterized in that it is divided into a plurality of pieces in the width direction to form a goodwill shape.

The squeegee (5 in FIG. 2) used for screen-printing solder (8 in FIG. 4) on the printed circuit board (7 in FIG. 1) of the present invention has a plurality of rows of front ends (in FIG. 2). 1
0) is provided, and each of these tips is divided into a large number in the width direction by a large number of cuts (11 in FIG. 2) to form a hot-spot shape.

The squeegee (5 in FIG. 2) used for screen-printing solder (8 in FIG. 4) on the printed circuit board (7 in FIG. 1) of the present invention has a plurality of rows of front ends (see FIG. 2). 1
0) is provided, and each of these tips is divided into a large number in the width direction by a large number of cuts (11 in FIG. 2) to form a hot-spot shape.
It is characterized in that the cuts of adjacent tips are staggered in a staggered manner.

According to the solder printing method of the present invention, an opening (size 7) provided at a position corresponding to the pre-attached component is formed on a printed circuit board (7 in FIG. 1) on which the pre-attached component is already mounted. A metal screen (1 in FIG. 1), which is provided with 2) in FIG. 1 and whose opening is covered with a stretchable thin film (3 in FIG. 1), is placed, and solder (FIG. 1) is placed on the metal screen. 4 of 8), and supply the squeegee (Fig. 2).
5) is moved on the metal screen.

According to the solder printing method of the present invention, an opening (a size of 7) in FIG. 1 on which a prefabricated component is already mounted is provided in a position corresponding to the prefabricated component and through which the prefabricated component passes. A metal screen (1 in FIG. 1), which is provided with 2) in FIG. 1 and whose opening is covered with a stretchable thin film (3 in FIG. 1), is placed, and solder (FIG. 1) is placed on the metal screen. 4 of 8) is supplied and the tip (1 in FIG. 2) is supplied.
It is characterized in that the squeegee (5 in FIG. 2), which is formed by dividing 0) into a large number in the width direction by a large number of cuts (11 in FIG. 2), is moved on the metal screen.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing a state in which a metal screen 1 used in the solder printing method according to the embodiment of the present invention is placed on a printed board.

In FIG. 1, the metal screen 1 is placed on a printed board 7. On the metal screen 1,
In addition to the SMT component opening 4 for soldering the leads of the SMT component to be attached to the printed board 7 later, an opening 2 (shown by a broken line) for preventing interference with a bare chip previously attached to the printed board 7. Is provided. The SMT component opening 4 is provided at a position corresponding to a pad to which a lead or the like of the SMT component on the printed board 7 is soldered. The opening 2 is provided at a position corresponding to the bare chip mounted on the printed board 7, and has a sufficient size to allow the bare chip to pass through with a margin.

The opening 2 is covered with a stretchable rubber-like thin film 3 so as to mask the bare chip and the printed board 7 around the bare chip during solder printing.

2 (a), 2 (b) and 2 (c) are front views of a squeegee used in the solder printing method of the present invention, respectively.
It is a bottom view and a side view.

Although the squeegee is generally composed of one plate, as shown in FIG. 2, the squeegee 5 in this embodiment is used.
Is provided with a body 9 made of a rigid member and two rows of tips 10 made of an elastic member. Each tip 10 of the squeegee 5 is provided with a vertical cut 11 at intervals of several mm.
Even if the metal screen 1 has a raised convex portion by arranging it in the shape of goodwill, only the portion of the tip 10 that abuts the convex portion is greatly bent and squeezing can be performed so as to escape the convex portion. Moreover, the cuts 11 of the tips 10 in the two rows are arranged in a staggered manner.

Next, the operation of the embodiment of the present invention will be described with reference to the drawings.

When the metal screen 1 is positioned and placed on the printed board 7, the thin film 3 covers and masks the bare chip previously attached to the printed board 7. The bare chip raises the thin film 3 and the convex portion is formed as shown in FIG. 6 is formed. Other parts such as the periphery of the SMT component opening 4 of the metal screen 1 are in close contact with the printed board 7.

Next, the solder paste 8 is supplied onto the metal screen 1, and the squeegee 5 is moved from one side of the metal screen 1 to the opposite side while pressing the tip 10 against the metal screen 1 as shown in FIG. , Squeeze the solder paste 8 and supply it to the SMT component opening 4.
Solder is printed on the pads on the printed board 7.

The tip 10 of the squeegee 5 is a few millimeters in the shape of a warm screen.
By dividing into width, even if the convex portion 6 exists,
Only the portion of the tip 10 that hits the convex portion 6 is largely elastically deformed to escape the convex portion 6, and the other portion of the squeegee 5 crawls on the metal screen 1 in a normal deformed state to perform uniform solder printing. Can be done.

Since the tip 10 of the squeegee 5 is finely divided into the shape of a goodwill, even if the convex portion has various sizes and various positions, only the portion corresponding to the convex portion of the tip 10 is present. It is elastically deformed so as to escape the convex portion and can be applied to a printed board on which various bare chips are preliminarily attached, which is versatile. Moreover, since the cuts 11 of the two rows of the tips 10 are arranged in a zigzag manner, the solder paste 8 on the metal screen 1 can be reliably squeezed, and the printing accuracy is improved.

In the solder printing method, metal screen, and squeegee of the present invention, high-density mounting of components has become mainstream in recent years, aiming at higher speed, lighter weight and smaller size of products using MCM and the like. COB (Chip O
It is a useful technique in the flip-chip mounting technique such as (n Board).

In the metal screen of the present invention, the opening 2 is provided to escape the previously mounted bare chip, and the thin film 3 having elasticity is stretched over the opening 2, so that the convex portion 6 can be made as low as possible. That is, in the metal mask for printing described in Japanese Patent Application Laid-Open No. 7-290851, a convex portion is provided on the metal mask itself made of a rigid member so as not to interfere with the parts to be preliminarily mounted. In order to deal with variations in dimensions and their mounting dimensions, it is necessary to set the highest height of the convex parts as the height of the convex parts. You have to keep it high. On the other hand, since the thin film 3 of the present invention sticks to the upper surface of the bare chip previously attached, if the thickness of the thin film 3 is ignored, the convex portion 6 becomes the same as the height of the bare chip previously attached, so that the convex portion 6 can be formed within a possible range. Can always be the lowest. Since the protrusion 6 can be lowered, the deformation of the portion of the tip 10 of the squeegee 5 that hits the protrusion 6 can be reduced, and the influence of the protrusion 6 on squeezing can be further reduced.

Further, the metal screen 1 is provided on the printed circuit board 7
When not set on, the metal screen 1 becomes flat and the metal screen 1 is thin as a whole. On the other hand, JP-A-7
In the metal mask described in Japanese Patent No. 290851, even when the convex portion is removed from the pudding and the substrate, the shape of the convex portion is not flattened and the metal mask is thick as a whole. Therefore, the metal screen 1 in the present embodiment can be stored in a space smaller than that of the metal mask disclosed in JP-A-7-290851 when not in use.

Further, the present invention is not limited to the two rows of squeegee tips, and may be three rows or more or only one row. The cuts at the tips of the two rows of the squeegee are not limited to the staggered arrangement, and various arrangements are possible.

[0029]

According to the solder printing method of the present invention, solder can be easily printed by using a metal screen and a squeegee in order to mount additional components on a printed circuit board on which components to be attached in advance are already mounted. it can.

Further, in the metal screen of the present invention, by masking the preliminarily attached component with a stretchable thin film, the convex portions caused by the preliminarily attached component can be made as low as possible,
The influence of squeezing due to this convex portion can be reduced.

In the squeegee of the present invention, by making the tip of the squeegee the shape of the convex portion formed on the metal screen regardless of the size and position of the component preliminarily attached to the printed board. Also, solder printing is possible regardless of the position, and there is versatility that it can be used regardless of the type of printed board.

[Brief description of drawings]

FIG. 1 is a plan view showing a state in which a metal screen 1 used in a solder printing method according to an embodiment of the present invention is placed on a printed board 7.

2 (a), (b) and (c) are respectively a front view, a bottom view and a side view of a squeegee 5 used in the solder printing method according to the embodiment of the present invention.

FIG. 3 is a partial perspective view of the metal screen 1 of FIG.

FIG. 4 is a perspective view showing a state where the metal screen 1 shown in FIG. 3 is squeezed by the squeegee 5 shown in FIG.

[Explanation of symbols]

1 metal screen 2 openings 3 thin film 4 SMT component opening 5 squeegee 6 convex 7 printed circuit boards 8 Solder paste 9 body 10 Tip 11 breaks

Claims (6)

[Claims] 1. A metal screen used for screen-printing solder for further mounting a post-mounting component on a printed circuit board on which the pre-mounting component is already mounted, wherein the pre-mounting component is provided at a position corresponding to the pre-mounting component. A metal screen comprising an opening sized to pass through and a stretchable thin film stretched so as to close the opening. 2. A squeegee used for screen-printing solder on a printed board, characterized in that the tip is divided into a number of cuts in the width direction by a number of cuts to form a goodwill screen. 3. A solder is screen-printed on a printed circuit board, characterized in that a plurality of rows of front end portions are provided in the front-rear direction, and each of these front end portions is divided into a plurality of pieces in the width direction by a plurality of cuts to form a well screen. A squeegee used for. 4. A plurality of rows of tips are provided in the front-rear direction, and each of these tips is divided into a number of widthwise directions by a number of cuts to form a hot-spot shape, and the cuts of adjacent tips are staggered in a staggered manner. A squeegee used for screen-printing solder on a printed circuit board characterized by the above. 5. A thin film, which is provided at a position corresponding to the prefabricated component and has a size through which the prefabricated component can pass, is provided on the printed board on which the prefabricated component is already mounted, and which has a stretchable thin film. A solder printing method comprising placing a closed and closed metal screen, supplying solder onto the metal screen, and moving the squeegee on the metal screen. 6. A thin film, which is provided at a position corresponding to the prefabricated component and has a size that allows the prefabricated component to pass through, is provided on the printed board on which the prefabricated component has already been mounted, and which has a stretchable thin film. Place a closed metal screen on which a squeegee is placed, supply solder onto this metal screen, and divide the tip into a large number in the width direction by multiple cuts to move the squeegee on the metal screen. And a solder printing method.