JP2006114658A - Printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a solder bridge from occurring on a printed wiring board of such a shape for connecting a soldered land and a solder-wetted land on a flat package IC via a thin line. <P>SOLUTION: A soldered land at the tail of rear soldered lands 9 and a rear solder-wetted land 11 are connected via a thin printed wiring connection bridge 13, whereby solder melted on the soldered land at the tail of the rear soldered lands 9 can easily transit to the land 9 along the connection bridge 13 between the soldered land and the rear solder-wetted land with low surface tension. Thus, no solder reservoir occurs at the tail of the soldered lands 9, resulting in preventing a solder bridge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solder dip soldering method for a four-way lead flat package IC using a solder dip bath as a soldering method.

  Conventionally, a printed wiring board in which this kind of four-way lead flat package IC is attached to a predetermined soldering land formed on the printed wiring board by a solder dip method is arranged in advance by arranging solder land groups in advance of the solder dip of the printed wiring board. From each land of the front soldering land group so as to be inclined so that one corner is at the head with respect to the direction and at the rear position of the front soldering land group with respect to the traveling direction of the solder dip Place the large side soldering lands at the rear corners of the front soldering land group, and further from each land of the rear soldering land group so that it is at the rear position of the rear soldering land group with respect to the solder dip traveling direction Prepare a printed wiring board on which a large rear soldering land is formed, and put the printed wiring board in front of the surface on which the soldered lands are formed. After mounting the IC, the printed wiring board is transported to a solder dip device in a preset soldering direction, and the IC mounting surface is melted to bring the IC solder surface down, It is characterized in that the IC is brought into contact from the front to the back and soldered (for example, see Patent Document 1).

FIG. 5 shows a conventional printed wiring board described in Patent Document 1. In FIG. As shown in FIG. 5, the printed circuit board 1 includes a rear soldering land group 3, a rear soldering land 5, and a four-direction lead flat package IC 6.
Japanese Patent No. 2635323

  However, in the conventional configuration, when an IC package that has been further densified in recent years is used, the soldered land shape of the conventional printed wiring board is called a solder bridge, and the solder between the IC lead terminals generated by the surface tension of the solder is used. It had the problem of frequent shorts.

  The present invention solves the above-described conventional problems, and can provide a soldering land shape for preventing the occurrence of solder bridges by an inexpensive method, reducing reworking of soldering, and improving production efficiency. An object is to provide a printed wiring board in which improvement and quality are stabilized.

  In order to solve the above-mentioned conventional problems, the printed wiring board of the present invention connects the rearmost soldering land and the rear soldering land of the rear soldering land group with a thin printed wiring, and the rear soldering. The land has a soldered land shape in which the electrode is divided into two or more.

  This explains how the problem has been solved. The mounting surface of the IC is conveyed with the solder surface down into the molten and jetted solder of the soldering apparatus. When the solder is slowly transported from the front to the rear of the IC glued to the printed wiring board in advance, the portion where the solder bridge is most likely to occur is at the end of the printed circuit board in the traveling direction. When the soldering land of the IC travels in the jet solder, the surface tension of the solder works backward in the direction of travel, so it is difficult for solder bridges to form in the forward direction of travel, whereas the last is the last The molten solder remaining on the land loses its place and stays, generating a solder bridge. Therefore, as shown in the conventional patent example, the rearmost soldering land at the end increases the amount of solder that can be retained by increasing the land area, thereby preventing the solder bridge with the last soldering land. I had. However, in recent miniaturized IC packages, the area of the soldering land has been reduced in accordance with the package size, so the problem cannot be solved sufficiently with the shape shown in the conventional patent example. In the printed wiring board of the present invention, the soldering land at the rearmost part of the rear soldering land group and the rear soldering land are connected by a thin printed wiring. Due to this thin printed wiring, the molten solder of the soldering land at the end of the rear soldering land group of the IC package moves on the thin printed wiring between the soldering land and the rear soldering land with a low surface tension. Thus, it is possible to easily shift to the rear soldering land. In this way, since no solder pool is generated at the rearmost part of the rear soldering land group, solder bridges can be prevented.

  The printed wiring board of the present invention is the printed wiring board according to claim 1, wherein the soldering land at the rearmost part of the front soldering land group and the side soldering lands are connected by a thin printed wiring. Therefore, even in the side soldering land, which is generally more difficult to increase the area, the solder bridge can be prevented even if the area is small.

  The printed wiring board of the present invention can effectively prevent a solder bridge with a wiring shape that can be easily realized and a minimum soldering area.

  In the first invention, a four-direction lead flat package IC, a printed wiring board, and an array of solder lands are previously arranged on the printed wiring board. Side soldering lands larger than each land of the front soldering land group at the rear position of the front soldering land group with respect to the traveling direction of the solder dip, and the rear soldering land group A rear soldering land larger than each land of the rear soldering land group is provided at a rear position of the rear soldering land group at the rear corner with respect to the solder dip traveling direction, and the last solder of the rear soldering land group is provided. The soldering land and the rear soldering land are connected by a thin printed wiring, and the rear soldering land is divided into two or more electrodes. By using a printed wiring board in the form of a wire, the melted solder of the soldering land at the end of the rear soldering land group of the IC package is placed on the thin printed wiring between the soldering land and the rear soldering land. By moving with low surface tension and easily shifting to the rear soldering lands, no solder pool is generated at the rearmost part of the rear soldering lands, and solder bridges can be prevented. Further, the wiring shape can be easily realized, and the area of the solder land can be reduced. If the rear soldering land is divided into two or more parts, other electrical wiring can pass through the center of the rear soldering land, and there is an effect that the wiring design is facilitated.

  In the printed circuit board according to the first aspect of the present invention, in particular, in the printed wiring board of the first aspect, the configuration in which the soldering land at the rearmost part of the rear soldering land group and the rear soldering land are connected by thin printed wiring is provided. The area of the soldering land group is generally increased by connecting the soldering lands at the end of the soldering lands and the side soldering lands with thin printed wirings to obtain the printed wiring board according to claim 2. In the side soldering land, which is more difficult, solder bridge can be prevented even if the area is small.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a shape of an IC solder land of a printed wiring board in the first embodiment of the present invention.

  A four-direction lead flat package IC 12 as shown in FIG. 2 is used, and soldered forward on the printed circuit board 7 of FIG. 1 corresponding to the lead portions of the terminals of the four-direction lead flat package IC 12. The wiring of the land group 8 and the rear soldering land group 9 is printed. A side soldering land 10 is formed between the front soldering land group 8 and the rear soldering land group 9, and a rear soldering land 11 is formed at the end of the rear soldering land group 9. The printed wiring is configured so as to bridge between the rearmost soldering land group 9 and the rear soldering land 11 with a thin printed wiring connection bridge 13.

  The operation and action of the printed wiring board configured as described above will be described below.

  First, in FIG. 3, the mounting surface of the four-way lead flat package IC 12 is arranged on the lower surface of the printed wiring board 7 and is slowly conveyed into the molten solder jet 14 ejected from the solder chimney 15 of the soldering apparatus. To do. When the solder package 14 is slowly conveyed from the front of the flat package IC 12 to the rear, the portion where the solder bridge is most likely to occur is in the rear of the printed circuit board. That is, a solder bridge is likely to occur between the rearmost soldering land group 9 in FIG. 1 and the rear soldering land 11. When the soldering land group of the flat package IC 12 travels in the jet solder as shown in FIG. 3, the surface tension of the solder is pulled by the solder jet 14 and works backward in the traveling direction. Therefore, solder bridges are unlikely to occur in front of the traveling direction, but when the last part is away from the solder jet 14, the molten solder remaining in the last land loses its place and stays to generate solder bridges. Therefore, as shown in the conventional patent example, the rear soldering land at the rear end increases the amount of solder that can be retained by increasing the land area and secures a certain amount of surface tension. It had a function to prevent the solder bridge. However, in recent IC packages that are becoming increasingly finer, the shape shown in the conventional patent example cannot sufficiently solve the problem. In the printed wiring board of the present invention, as shown in FIG. 1, the rearmost soldering land group 9 and the rear soldering land 11 are connected by a thin printed wiring connection bridge 13. By the thin printed wiring connection bridge 13 of the rear soldering land, the molten solder on the soldering land at the rearmost part of the rear soldering land group 9 is connected to the thin printed wiring between the soldering land and the rear soldering land. The bridge 13 can be moved to the rear soldering land 9 by moving with a low surface tension. With such a configuration, no solder pool is generated at the rearmost part of the rear soldered land group 9, and solder bridges can be prevented.

  As described above, in the present embodiment, a wiring connection bridge is configured by thin printed wiring between the soldering land at the rearmost part of the rear soldering land group of the four-way lead flat package IC and the rear soldering land. Thus, no solder pool is generated at the last part of the rear soldering land group, and solder bridges can be prevented.

  Further, in the present embodiment, since the solder bridge prevention effect can be realized by the rear soldering land having a smaller area than the conventional one, an unnecessary area is reduced, and there is also an effect of improving the mounting density of components. Furthermore, the amount of unnecessary solder necessary for the rear soldering land can be reduced while being small.

(Embodiment 2)
FIG. 4 is a shape diagram of an IC solder land of the printed wiring board according to the second embodiment of the present invention.

  On the printed circuit board 7 in FIG. 4, the side soldering lands 10 are narrow between the front soldering land groups 8 and the side soldering lands 10 corresponding to the lead portions of the terminals of the four-way lead flat package IC12. The printed wiring is formed so as to be bridged by the printed wiring connection bridge 16.

  The operation and action of the printed wiring board configured as described above will be described below.

  As described in the first embodiment, the portion where the solder bridge is likely to occur is not between the rearmost soldering land group 9 and the rear soldering land 11 in FIG. 1, which is the front soldering land group. 8 between the rearmost 8 and the side soldering lands 10. The solder bridge prevention mechanism is a thin print between the soldering land at the end of the front soldering land group 8 and the side soldering land 10 as shown in FIG. By connecting with the wiring connection bridge 16, the molten solder on the soldering land at the rearmost part of the front soldering land group 8 passes through the thin printed wiring connection bridge 16 between the soldering land and the side soldering land. By moving with low surface tension and easily shifting to the side soldering lands 10, no solder pool is generated at the end of the front soldering land group 8, and solder bridges can be prevented.

  As described above, in the present embodiment, a wiring connection bridge is formed by thin printed wiring between the soldering land at the end of the front soldering land group of the four-way lead flat package IC and the side soldering land. As a result, no solder pool is generated at the rearmost part of the front solder land group, and a solder bridge can be prevented.

  Further, in the present embodiment, since the solder bridge prevention effect can be realized by the rear soldering land having a smaller area than the conventional one, an unnecessary area is reduced, and there is also an effect of improving the mounting density of components. Furthermore, the amount of unnecessary solder necessary for the rear soldering land can be reduced while being small.

  As described above, the printed wiring board according to the present invention can effectively prevent solder bridging with a wiring shape that can be easily realized and a minimum soldering area. The present invention can also be applied to other parts other than an IC that performs soldering using a solder dip bath.

Shape diagram of IC solder land of printed wiring board in Embodiment 1 of the present invention Dimensional drawing of four-way lead flat package IC in Embodiment 1 of the present invention Explanatory drawing of operation | movement and effect | action in Embodiment 1 of this invention Shape diagram of IC solder land of printed wiring board in Embodiment 2 of the present invention IC solder land shape of conventional printed wiring board

Explanation of symbols

7 printed wiring board 8 front soldering land group 9 rear soldering land group 10 side soldering land 11 rear soldering land 12 4-way lead flat package IC
13 Thin printed wiring connection bridge with back soldering land 14 Molten solder jet 15 Solder chimney (soldering device)
16 Thin printed wiring connection bridge with side soldering lands

Claims (2)

A 4-direction lead flat package IC, a printed wiring board, and an array of solder lands in advance on the printed wiring board are inclined so that one corner is at the head with respect to the solder dip traveling direction of the printed wiring board. Solder at the rear soldering lands larger than each land of the front soldering land group at the rear position of the front soldering land group with respect to the traveling direction of the solder dip, and at the rear corner of the rear soldering land group A rear soldering land larger than each land of the rear soldering land group is provided at the rear position of the rear soldering land group with respect to the traveling direction of the dip, and the last soldering land and rear soldering of the rear soldering land group are provided. The lands are connected by thin printed wiring, and the rear soldering land has a soldering land shape in which the electrode is divided into two or more. Printed wiring board. A 4-direction lead flat package IC, a printed wiring board, and an array of solder lands in advance on the printed wiring board are inclined so that one corner is at the head with respect to the solder dip traveling direction of the printed wiring board. The side soldering lands larger than each land of the front soldering land group at the rear position of the front soldering land group with respect to the traveling direction of the solder dip, and the solder at the end of the side soldering land group The printed wiring board according to claim 1, wherein the attachment land and the side soldering land are connected by a thin printed wiring.

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