JPH04314389A - Electric component soldering method - Google Patents

Abstract

PURPOSE:To prevent the formation of solder balls caused by cream solder bleeding in a method for soldering various electronic components to a printed circuit board, for example, chip components, using cream solder and thereby prevent the degradation caused by solder balls. CONSTITUTION:The shape of the cream solder printed and coated on a conductor land 2 of a printed circuit board 1 is similar to the conductor land shape. A cut-away is formed in the inner side. Hence it is possible to greatly decrease the bleeding of cream solder when a chip component 3 is mounted and thereby to prevent the formation of solder balls during reflow. In this way, a high quality solder state can be realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for soldering electronic components to a circuit mounting board, in which chip components and the like are soldered and mounted on a printed circuit board using cream solder.

0002

BACKGROUND OF THE INVENTION In recent years, circuit mounting boards are becoming more dense and finer in order to achieve smaller size and lower costs. Furthermore, chip components are used for component carriers, and the soldering technique for these components is so-called surface mounting, in which reflow soldering is performed using cream solder.

[0003] Corrosive solder flux residue and solder balls generated during soldering are removed by cleaning the board, thereby ensuring quality.

A conventional soldering technique will be described below. 10 to 13 show a conventional soldering method. In FIG. 10, 1 is a printed circuit board, 2 is a conductor land provided on the printed circuit board, and 10
3 is cream solder printed on the land, 3 is a chip component mounted by a mounting machine, and 3a is an electrode portion of the chip component to be soldered.

The soldering process for the soldering points constructed as described above will be explained below.

In FIG. 10, a chip component 3 is mounted on a cream solder 10 printed and shaped on a conductor land 2 using a mounting machine, and heated at about 200° C. to 22° C. in a reflow oven.
The solder is melted after heating for about 30 seconds at a temperature around 0° C., and the electrode 3a of the component 3 and the conductor land 2 are connected by the solder.

[0007]

However, in the above conventional configuration, as shown in FIG. 11, the cream solder 10 formed by printing is broken by the pressing force of the chip component 3 during mounting, and the conductor land 2 The inter-electrode solder distance W narrows to w as it protrudes from the distance W. In FIG. 12, when the solder is melted, the melted and liberated solder 4 flows along the lower surface of the chip component 3 to form an aggregate 5 of liberated solder. Eventually, as shown in FIG. 13, a force F acts on the chip component 3 due to the weight of the chip component 3 and the wetting of the molten solder 4 to the surface of the electrode 3a, and the distance between the printed circuit board 1 and the chip component 3 becomes extremely small. The loose solder 5 moves to the side surface of the chip component 3 and forms a spherical solder mass 6 (hereinafter referred to as a solder ball).
It adheres to the vicinity of the chip component 3. It is said that in electronic equipment that incorporates a printed circuit board with chip components, etc. mounted, the solder balls 6 may come off from the vicinity of the chip component 3 due to vibrations during transportation or use, and adhere to between the surrounding microelectrodes, deteriorating the quality. It had some problems. The present invention solves the above conventional problems and aims to provide a highly reliable soldering method.

[0008]

[Means for Solving the Problems] In order to achieve this object, the soldering method of the present invention involves applying a cream solder to a part of the inner side of a solder shape, which is supplied onto a land on which a chip component provided on a printed circuit board is soldered. Cut it out in the specified shape.
It is configured to supply mu solder.

[0009]

[Function] With this configuration, it is possible to reduce the supply of excess cream solder and prevent the generation of solder balls, etc.
It is possible to significantly improve the reliability of printed circuit boards.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

In FIG. 1, 1 is a printed circuit board;
2 is a conductor land provided on a printed circuit board, 11 is cream solder applied to the land in a concave shape, 3 is a mounted chip component, and 3a is an electrode of the chip component.

The soldering process for the soldering points constructed as described above will be explained with reference to FIGS. 2 to 4.

In FIG. 2, the chip component 3 is mounted by a mounting machine with a predetermined pressing force P onto the cream solder 11 printed in a concave shape on the conductor land. The cream solder 11 printed in a concave shape in FIG. Since the notch is located inside the conductor land 2, the solder does not protrude beyond the end face of the wiring foil.

As a result, as shown in FIG. 4, when the solder melts, it is under the influence of the surface tension of the solder, so the solder does not come loose and no solder balls are generated.

FIG. 5 shows a second embodiment of the present invention.
1 is a printed circuit board, 2 is a conductor land, 12 is cream solder, 3 is a chip component, 3a is an electrode of the chip component,
The above configuration is similar to the configuration shown in FIG. The same applies to other embodiments described below. In Figure 5,
The difference from the configuration shown in FIG. 1 is that the shape of the supplied cream solder is changed from a concave shape to a U shape. FIG. 6 shows a third embodiment of the present invention, which differs from the structure shown in FIG. 1 in that the shape of the supplied cream solder is changed from a concave shape to a V shape. FIG. 7 shows a fourth embodiment of the present invention, which differs from the configuration in FIG. 1 in that the corners of the conductor lands are rounded. FIG. 8 shows a fifth embodiment of the present invention, which differs from the configuration in FIG. 1 in that the corners of the conductor lands are rounded and the shape of the supplied cream solder is changed from a concave shape to a U shape. This is the point I made. FIG. 9 shows a sixth embodiment of the present invention, which differs from the configuration shown in FIG. 1 in that the corners of the lands are rounded and the shape of the supplied cream solder is changed from a concave shape to a V shape. This is the point. As described above, according to the embodiments of the present invention, there is very little protrusion or bleeding of cream solder when a chip component is pressed, and the soldering quality is stabilized. In the above embodiments, it goes without saying that any shapes other than those in the embodiments may be used for the shape of the recessed portion and the shape of the cream solder printing.

[0016]

Effects of the Invention As described above, the present invention provides a solder cream that is supplied onto a land on which a chip component provided on a printed circuit board is soldered. By supplying solder, it is possible to achieve high quality soldering of chip components without the generation of solder balls.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a soldering method in a first embodiment of the present invention.

FIG. 2 is a side view of the first embodiment of the present invention after solder printing and immediately before parts are mounted.

FIG. 3 is a side view of a state in which components are mounted after solder printing in the first embodiment of the present invention.

[Fig. 4] Side view after solder connection in the first embodiment of the present invention

FIG. 5 is a plan view of the state after solder printing in the second embodiment of the present invention.

FIG. 6 is a plan view of the state after solder printing in the third embodiment of the present invention.

FIG. 7 is a plan view of the state after solder printing in the fourth embodiment of the present invention.

FIG. 8 is a plan view of the state after solder printing in the fifth embodiment of the present invention.

FIG. 9 is a plan view of the state after solder printing in the sixth embodiment of the present invention.

[Figure 10] Side view of the state immediately before mounting components after conventional solder printing

[Figure 11] Side view of parts mounted after conventional solder printing

[Figure 12] Side view of conventional solder melting state

[Figure 13] Side view of the state after conventional solder connection

[Explanation of symbols]

1 Printed wiring board 2 Conductor land 3 Chip parts 4 Melted solder 5. Loose solder 6 Solder ball 11 Concave cream solder (1) 12 U-shaped cream solder (1) 13 V-shaped cream solder (1) 14 Concave cream solder (2) 15 U-shaped cream solder (2) 16 V-shaped cream solder (2) 21 Concave cutout (1) 22 U-shaped notch (1) 23 V-shaped notch (1) 21 Concave cutout (2) 22 U-shaped notch (2) 23 V-shaped notch (2) 3a　Chip component electrodes

Claims (4)

[Claims] 1. Cream solder is supplied onto a conductor land provided on a printed circuit board in a shape that is roughly similar to the conductor land and a part of the inside of the conductor land is cut out, and the cream solder is applied onto the conductor land. A method for soldering electronic components, which comprises mounting electronic components such as chip components and then heating and soldering them under predetermined conditions using a solder reflow oven. 2. The method of soldering electronic components according to claim 1, wherein the cream solder shape with a part of the inner side cut out has a concave shape. 3. The method of soldering electronic components according to claim 1, wherein the cream solder has a U-shape with a portion of the inside cut out. 4. The method of soldering electronic components according to claim 1, wherein the cream solder has a V-shape with a portion of the inside cut out.