JP4454568B2 - Printed wiring board - Google Patents

Description

  The present invention relates to a printed wiring board on which a four-way lead flat package IC is mounted using a solder dip method.

  As electronic devices become smaller and lighter, printed wiring board components are required to be miniaturized, and four-way lead flat package ICs are often used. When the four-way lead flat package IC is mounted on the printed wiring board, the four-way lead flat package IC is temporarily fixed to the printed wiring board with an adhesive. Thereafter, the four-way lead flat package IC is printed by a flow soldering method (hereinafter referred to as a solder dip method) in which the printed wiring board is passed through a solder dip bath and the four-way lead flat package IC is soldered to the printed wiring board. Soldered to the board.

  In the four-direction lead flat package IC, there is a problem that a solder bridge is generated between the leads because the distance between the leads of the IC is short. When a short circuit occurs between the leads due to the solder bridge, it is necessary to perform a correction operation to remove the short circuit. Alternatively, it is necessary to take measures such as mounting the four-way lead flat package IC manually by an operator without using the solder dipping method, and the production efficiency is lowered.

  Various substrates have been proposed as printed wiring boards to which the four-way lead flat package IC is soldered by the solder dip method. In Patent Document 1, four groups of solder lands are formed corresponding to the four directions of leads (leads extending from four sides) of the four-direction lead flat package IC. A printed wiring board is described that is inclined 45 ° with respect to the soldering direction, that is, the traveling direction of the printed wiring board in the solder dip bath. Further, in the printed wiring board, a side soldering land larger than each land of the front soldering land group is formed between the front soldering land group and the rear soldering land group, and the rear part of the rear soldering land group In addition, a rear soldering land larger than each land of the rear soldering land group is formed.

  Further, in Patent Document 2, between the front soldering land group and the rear soldering land group and between the two rear soldering land groups, the soldering land group has substantially the same width, A printed wiring board on which a plurality of soldering lands are formed is described.

JP 63-213994 A (2nd page, lower left column and lower right column, FIG. 1) Japanese Utility Model Publication No. 4-20263 (page 5, FIG. 3)

  In the printed wiring board described in Patent Document 1, the side soldering lands and the rear soldering lands are larger than other lead lands. For this reason, when soldering is performed by the solder dipping method, the solder swells on the side soldering lands and the rear soldering lands, and the swelled solder adheres to the adjacent lead lands, which may cause a so-called solder bridge.

  Moreover, in the printed wiring board described in Patent Document 2, since the side soldering lands and the rear soldering lands are formed of a plurality of soldering lands, the solder bridge is reduced. However, also in this case, when the soldering is finished and the printed wiring board is stopped, the surface tension, which is a resistance force against the return of the solder, is weak, so that a solder bridge may be generated. That is, the soldering effect by the side soldering lands and the rear soldering lands is not sufficient.

  The present invention is an invention for solving the above-described problems, and an object thereof is to provide a printed wiring board capable of enhancing the soldering effect and preventing the formation of a solder bridge.

The printed wiring board according to the present invention is formed corresponding to the leads of the four-way lead flat package IC, and is composed of two groups of front solder lands and two groups of rear solder lands inclined with respect to the soldering direction. A plurality of side soldering lands provided between the front soldering land group and the rear soldering land group, and a plurality of rear soldering lands provided between the rear soldering land groups. In the wiring board, each of the plurality of rear soldering lands is formed in a band shape and is disposed along the soldering direction (for example, aligned with the soldering direction) . A first rear soldering land (for example, a rear soldering land) formed in a curved shape having a convex portion on the rear side in the soldering traveling direction and provided at a position closest to the rear soldering land group. a) Two sides of the portion where the four-direction lead flat package IC is placed, an extension of a line connecting the leading ends of lands included in one rear soldering land group, and the other rear soldering land group It is provided in the area | region enclosed with the extended line of the line which connects the front- end | tip part of the contained land .

  The side soldering lands are preferably formed in a rectangular shape and arranged so that the longitudinal direction is orthogonal to the soldering direction.

  The length of the side soldering land provided in the vicinity of the front soldering land group is longer than the length in the longitudinal direction of the side soldering land provided in the vicinity of the rear soldering land group. It is preferable that the film is formed in a long state.

  According to the present invention, each of the plurality of rear soldering lands is formed in a band shape and arranged along the soldering direction, so that a smooth solder flow can be created by the plurality of rear soldering lands. As a result, the formation of a solder bridge can be more effectively prevented.

Embodiment 1 FIG.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an example of a printed wiring board according to the first embodiment of the present invention. As shown in FIG. 1, four groups of solder lands are formed on the printed circuit board 1 corresponding to the leads of the four-way lead flat package IC. The four groups of solder land groups include two groups of front solder land groups 2 and two groups of rear solder land groups 3. Each of the front soldered land group 2 and the rear soldered land group 3 includes lands soldered to the leads of the four-way lead flat package IC. The front soldering land group 2 and the rear soldering land group 3 are arranged so that the direction of the line connecting the tips of the leads in each group is inclined 45 degrees with respect to the soldering direction of the printed wiring board 1. ing. In the four-direction lead flat package IC, an intersection point between an edge where a lead soldered to one front soldering land group 2 and a side where a lead soldered to the other front soldering land group 2 comes out is an intersection X To do. Further, the intersection of the side where the lead soldered to one rear soldering land group 3 and the side where the lead soldered to the other rear soldering land group 3 comes out in the four-direction lead flat package IC is an intersection. Y. In this case, the soldering progress direction can be defined as a direction from the intersection Y to the intersection X, for example.

  Further, a side soldering land group 4 is provided between the front soldering land group 2 and the rear soldering land group 3. FIG. 2 is a plan view showing an example of the side soldering land group 4 in detail. The side soldering land group 4 includes a plurality of strip-shaped side soldering lands 4a. The plurality of side soldering lands 4a are arranged in a fan shape. By arranging in a fan shape, the solder flows smoothly from the front solder land group 2 to the rear solder land group 3.

  FIG. 3 is an explanatory view showing an arrangement region of the side soldering land group 4. The side soldering land group 4 includes an extension of a line connecting the front end portions of the lands included in the front soldering land group 2 between the front soldering land group 2 and the rear soldering land group 3, and a rear soldering. It is provided in the arrangement area 10 surrounded by the extended line connecting the tips of the lands included in the attached land group 3, that is, in the hatched area in FIG. By arranging the side soldering land group 4 in the arrangement region 10, the solder of the front soldering land group 2 can flow smoothly to the rear soldering land group 3.

  Further, as shown in FIG. 1, a rear soldering land group 5 is provided between the left and right rear soldering land groups 3 that form the rear corner portion in the soldering direction. The rear soldering land group 5 includes strip-shaped rear soldering lands 5a, 5b, and 5c. The rear soldering lands 5a, 5b, and 5c are formed in a “shape” having a protrusion on the rear side in the soldering direction.

  FIG. 4 is an explanatory view showing an arrangement region of the rear soldering lands 5a. A rear soldering land 5a provided at a position closest to the rear soldering land group 3 is included in the left rear soldering land group 3 on the left side of the portion where the four-direction lead flat package IC 6 is placed. 4 is an extension line of the line connecting the tip ends of the lands and the extension area of the line connecting the tip ends of the lands included in the right rear soldering land group 3, that is, the hatched area shown in FIG. It is provided in the inside. The rear soldering lands 5a are arranged in the arrangement region 20, so that the solder of the rear soldering lands 3 can be drawn smoothly.

Hereinafter, the soldering operation will be described.
A four-way lead flat package IC 6 is temporarily fixed to the printed wiring board 1 with an adhesive (not shown). Thereafter, the printed wiring board 1 is passed through a solder dip bath (not shown), and the four-way lead flat package IC 6 is soldered to the printed wiring board 1.

  At the time of soldering, the side soldering land group 4 takes away the excess solder from the front soldering land group 2 and flows the solder to the rear soldering land group 3. Since the side soldering land group 4 is composed of a plurality of soldering lands 4a, it is possible to prevent the solder from rising greatly. Furthermore, excess solder from the rear soldering land group 3 is taken up by the rear soldering land group 5.

  FIG. 5 is an explanatory view showing the flow of solder to the rear soldering land group 5. The solder flows through the rear soldering lands 3a in the rear soldering lands 3 to the rear soldering lands 5a, 5b, and 5c. The rear soldering lands 5a, 5b, and 5c are formed in a “shape” having a protrusion on the rear side with respect to the soldering direction, and therefore flow from the left and right rear soldering lands 3. The solder joins at the center of the first rear soldering land 5a, increases the momentum, and further flows to the rear rear soldering land 5b and the rear soldering land 5c. For this reason, solder does not overflow from the first rear soldering land 5a.

Further, the rear soldering land 5b and the rear soldering land 5c absorb the solder that could not be drawn by the first rear soldering land 5a. As described above, since the plurality of independent rear soldering lands 5a, 5b, and 5c are provided, it is possible to prevent formation of a solder bridge between the soldered lands.

  FIG. 6 is an explanatory diagram showing a case where the solder bridge 30 is generated between the side soldering lands 4a. That is, the side soldering lands 4a take the solder of the front soldering lands 2a, and are explanatory views showing a case where a solder bridge 30 is generated between the side soldering lands 4a. The solder bridge 30 is not electrically connected to the front soldering land 2a and the rear soldering land 3a. For this reason, even if the solder bridge 30 is generated between the side soldering lands 4a, it is not necessary to perform a correction operation or the like, and the efficiency of mounting the four-way lead flat package IC can be improved. Further, since the side soldering lands 4 include a plurality of side soldering lands 4a, it is possible to prevent the formation of solder bridges between the soldered lands.

  FIG. 7 is an explanatory view showing a case where the solder bridge 30 is generated between the rear soldering lands. That is, the solder from the rear soldering land group 3 is taken, and the solder bridge 30 is generated between the rear soldering land 5a and the rear soldering land 5b and between the rear soldering land 5b and the rear soldering land 5c. It is explanatory drawing which shows the case where it did. In this case, even if the solder bridge 30 is generated between the rear soldering land 5a and the rear soldering land 5b, or the solder bridge 30 is generated between the rear soldering land 5b and the rear soldering land 5c. However, it is not necessary to perform a correction operation for that purpose, and the efficiency of mounting the four-way lead flat package IC 6 can be increased. Further, since the rear soldering land group 5 includes a plurality of rear soldering lands, it is possible to prevent a solder bridge from being formed between the soldered lands.

  FIG. 8 is an explanatory diagram showing the movement of the solder when the soldering is finished and the movement of the printed wiring board is stopped. While the printed circuit board is moving in the soldering direction by the solder dipping method, the solder of the rear soldering lands 5a, 5b, and 5c is close to the point A. When the soldering is completed and the printed wiring board stops moving, the solder that has approached the point A returns to the direction of the arrow due to diffusion. Accordingly, it is possible to prevent the solder from rising in the rear soldering lands 5a, 5b, and 5c, and the rising solder from adhering to the nearby soldered land and soldering land to form a solder bridge.

  In the present embodiment, between the two groups of rear solder lands 3, the band-shaped solder-drawn lands having protrusions on the rear side with respect to the soldering progress direction extend along the soldering direction. Therefore, the solder flowing from the rear soldering land group 3 joins at the center of the first rear soldering land 5a, and the rear rear soldering land 5b and the rear soldering are further rearranged. It flows to the land 5c. Therefore, it is possible to prevent a solder bridge from being formed by excess solder remaining in the rear soldering land group 3.

  Further, in the present embodiment, the rear soldering lands 5a are provided in the arrangement region 20, so that the rear soldering lands 5a can smoothly draw the solder of the left and right rear soldering lands 3. .

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the shape of the rear soldering land group is different from the shape of the rear soldering land group in the first embodiment.

  FIG. 9 is a plan view showing an example of a printed wiring board according to the second embodiment of the present invention. As shown in FIG. 9, a rear soldering land group 7 is provided between the left and right rear soldering land groups 3 that form the rear corner portion in the soldering direction. The rear soldering land group 7 includes strip-shaped rear soldering lands 7a, 7b, 7c. The rear soldering lands 7a, 7b, 7c are formed in a “curved shape” having a convex portion on the rear side in the soldering direction.

  When soldering the four-way lead flat package IC 6 to the printed wiring board 1, the four-way lead flat package IC 6 is temporarily fixed to the printed wiring board 1 with an adhesive (not shown). Thereafter, the printed wiring board 1 is passed through a solder dip bath (not shown), and the four-way lead flat package IC 6 is soldered to the printed wiring board 1.

  At the time of soldering, the rear soldering lands 7a, 7b, 7c are formed in a “curved shape” having convex portions on the rear side with respect to the soldering progress direction. The flowing solder merges at the center of the first rear soldering land 7a, increases the momentum, and further flows to the rear rear soldering land 7b and the rear soldering land 7c. For this reason, the solder does not overflow from the rear soldering land 7a, and the solder that cannot be pulled by the rear soldering land 7a can be absorbed by the rear soldering land 7b and the rear soldering land 7c. In addition, since a plurality of independent rear soldering lands 7a, 7b, and 7c are provided, it is possible to prevent the formation of a solder bridge between the soldered lands.

  In the present embodiment, a plurality of curved strip-shaped soldering lands having protrusions on the rear side with respect to the soldering progress direction are provided between the two groups of rear soldering lands 3 along the soldering direction. Since the individual solders are arranged, the solder flowing from the rear soldering land group 3 merges at the center of the first rear soldering land 7a, and the rear rear soldering land 7b and the rear soldering land 7c. Flowing into. Therefore, it is possible to prevent a solder bridge from being formed by excess solder remaining in the rear soldering land group 3.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the shape of the side soldering land group is different from the shape of the side soldering land group in the first embodiment. FIG. 10 is a plan view showing an example of a printed wiring board according to the third embodiment of the present invention. FIG. 11 is a plan view showing an example of the side soldering land group in detail.

  A side soldering land group 8 is provided between the front soldering land group 2 and the rear soldering land group 3. The side soldering land group 8 includes a plurality of rectangular side soldering lands as shown in FIGS. Each side soldering land is disposed so that the longitudinal direction is orthogonal to the soldering direction. Even if the side soldering land group 8 is formed as shown in FIGS. 10 and 11, the solder flows smoothly from the front soldering land group 2 to the rear soldering land group 3.

  When the side soldering lands in the side soldering lands 8 are not orthogonal to the soldering progress direction, the longitudinal ends of the side soldering lands have protrusion-like corners. Solder tends to concentrate. For this reason, when the soldering is finished and the printed wiring board 1 is stopped, the surface tension which is a resistance force against the return of the solder is weak. On the other hand, when the side soldering lands in the side soldering land group 8 are orthogonal to the soldering direction, the side soldering is performed when the printed wiring board 1 is stopped. The whole of the land in the longitudinal direction becomes a resistance against the return of the solder. That is, the side soldering land group 8 exhibits a strong surface tension.

  In this embodiment, the side soldering lands in the side soldering land group 8 are arranged so that the longitudinal direction is perpendicular to the soldering progress direction, so that the soldering is finished and the printed wiring board is stopped. In this case, the resistance against the return of the solder can be increased, and the formation of a solder bridge between the soldered lands can be prevented.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described with reference to the drawings. The present embodiment is a case where the shape of the side soldering land group is changed in the first embodiment. Further, the present embodiment is different from the form of the side soldering land group of the third embodiment.

  FIG. 12 is a plan view showing another example of the side soldering land group in detail. A side soldering land group 9 is provided between the front soldering land group 2 and the rear soldering land group 3. The side soldering land group 9 includes a plurality of rectangular side soldering lands. The longitudinal direction of each side soldering land is arranged so as to be orthogonal to the soldering direction. More side soldering lands are provided on the front soldering land group 2 side than on the rear soldering land group 3 side. In the present embodiment, a side where the front soldering land 2a is provided (shown as a side of the four-direction lead flat package IC 6 in FIG. 12) and a side where the rear soldering land 3a is provided (in FIG. 12). If the line extending so as to be perpendicular to the soldering direction from the angle formed by the intersection with the four-direction lead flat package IC 6 is expressed as a center line, it is on the middle line and to the left and right of the center line. Three side soldering lands are provided, and in addition to that, two side soldering lands 9a are provided on the front soldering land group 2 side, whereas the rear soldering land group 3 side is provided. A configuration in which one side soldering land 9b is provided is shown. The length of the side soldering land 9a is longer than the length of the side soldering land 9b. That is, the side soldering land 9 a provided in the vicinity of the front soldering land group 2 has a length in the longitudinal direction of the side soldering land 9 b provided in the vicinity of the rear soldering land group 3. It is formed in a state longer than the length in the longitudinal direction. Further, the longitudinal center position of the side soldering lands 9a is higher than the longitudinal center position of the other side soldering lands 9a. Here, “high” means that the shortest distance from the line formed by the soldering direction passing through the corner formed by the intersection is long.

  In the present embodiment, since more side soldering lands 9a are provided on the front soldering land group 2 side, the side soldering land group 9 is used as the front soldering land group 2 during soldering. Can be drawn in smoothly. Moreover, as indicated by arrows in FIG. 12, it is possible to create a solder flow to the rear solder land group 3. Further, since the side soldering lands in the side soldering land group 8 are arranged so that the longitudinal direction is perpendicular to the soldering progress direction, when the soldering is finished and the printed wiring board 1 is stopped. The resistance against the return of solder can be increased, and the formation of a solder bridge between solder lands can be prevented.

  Further, since the position of the center in the longitudinal direction of the side soldering lands 9a is higher than the position of the center of the other side soldering lands in the longitudinal direction, as shown by the arrows in FIG. The flow of solder to the rear soldering land group 3 can be created smoothly.

  In addition, when creating a pattern of a plurality of soldering lands on a printed wiring board, an independent pad may be created, or it may be created by forming a pattern by removing a resist by exposure.

  In each of the above embodiments, the printed wiring board on which the four-way lead flat package IC 6 is mounted is taken as an example. However, the printed wiring board is a two-way lead flat package IC or the like, and the distance between the lead terminals is short. A plurality of strip-shaped soldering lands may also be provided for parts that have a problem with solder bridges.

  Furthermore, electronic components mounted on a printed wiring board are not only surface-mounted electronic components but also electronic components in which electronic component terminals are inserted into through holes of the printed wiring board and soldered on the back surface of the printed wiring board. May be. By providing a plurality of strip-shaped soldering lands on the printed circuit board, it can be expected that solder bridges can be prevented from being formed between the electronic component terminals.

  The present invention is applicable to a printed wiring board on which a four-way lead flat package IC is mounted using a solder dip method.

It is a top view which shows an example of the printed wiring board in the 1st Embodiment of this invention. It is the top view in which an example of the side soldering land group was shown in detail. It is explanatory drawing which shows the arrangement | positioning area | region of a side soldering land group. It is explanatory drawing which shows the arrangement | positioning area | region of the back soldering land 5a. It is explanatory drawing which shows the flow of the solder to a back soldering land group. It is explanatory drawing which shows the case where the solder bridge generate | occur | produced between the side soldering lands. It is explanatory drawing which shows the case where a solder bridge generate | occur | produces between back soldering lands. It is explanatory drawing which shows the motion of the solder at the time of stopping the motion of the printed wiring board at the time of completion | finish of soldering. It is a top view which shows an example of the printed wiring board in the 2nd Embodiment of this invention. It is a top view which shows an example of the printed wiring board in the 3rd Embodiment of this invention. It is the top view in which an example of the side soldering land group was shown in detail. It is the top view in which the other example of the side soldering land group was shown in detail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Front soldering land group 2a Front soldering land 3 Back soldering land group 3a Rear soldering land 4, 8, 9 Side soldering land group 4a, 9a, 9b Side soldering land 5, 7 Rear soldering lands 5a, 5b, 5c, 7a, 7b, 7c Rear soldering lands 6 4-way lead flat package IC
10, 20 Arrangement area 30 Solder bridge

Claims (3)

There are two groups of front soldering lands and two groups of rear soldering lands that are formed corresponding to the leads of the four-direction lead flat package IC and are inclined with respect to the soldering direction. A printed wiring board in which a plurality of side soldering lands are provided between the attached land group and the rear soldering land group, and a plurality of rear soldering lands are provided between the rear soldering land groups. ,
Each of the plurality of rear soldering lands is formed in a band shape and is disposed along the soldering direction ,
The rear soldering land is formed in a curved shape having a convex portion in the rear with respect to the soldering traveling direction,
The first rear soldering land provided at a position closest to the rear solder land group has two sides, one rear solder land group in a portion where the four-way lead flat package IC is placed. Characterized in that it is provided in an area surrounded by an extension line of a line connecting the tip ends of the lands included in and an extension line of a line connecting the tip ends of the lands included in the other rear soldered land group. Printed wiring board. Side solder drawing lands, formed in a rectangular shape, a printed wiring board according to claim 1 Symbol placement longitudinal direction is arranged so as to be perpendicular to the traveling direction soldering. The length of the side soldering land provided in the vicinity of the front soldering land group is longer than the length in the longitudinal direction of the side soldering land provided in the vicinity of the rear soldering land group. The printed wiring board according to claim 2 , wherein the printed wiring board is formed in a long state.

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