JP2000077839A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board in which the solder short circuit between lead can be surely prevented under easier controlling so as to prevent the occurrence of soldering nonconformance, even when a narrow-pitch four-way lead flat package IC is subject to soldering. SOLUTION: This printed wiring board 11 is provided with a forward soldered land group 12 which is inclined in a soldering advancing direction, a backward soldered land group 13 arranged on its rear side, a side solder plating land 14 that the last land of the forward soldered land group 12 between the sort-side land side of the forward soldered land group 12 and the backward soldered land group 13 is extended, and a backward soldered land 15 that the last land of the backward soldered land group 13 between the backward soldered land groups 13 is extended, and an individual soldered land 17 is made small in size, and further a four-way lead flat package is mounted to the printed wiring board 11 by soldering using a jet-type solder bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-way lead flat package I by soldering using a jet type solder bath.
C relates to a printed wiring board on which C is mounted.

[0002]

2. Description of the Related Art As the component mounting density of printed wiring boards is increasingly required to be fine, it is necessary to mount substrates such as four-way lead flat package ICs having a narrow pitch. Therefore, it is necessary to solder a four-way lead flat package IC or the like to a printed wiring board by a method that realizes an improvement in reliability without a short circuit due to solder between lead terminals and an improvement in production efficiency.

A conventional printed wiring board of this type, which is proposed in, for example, Japanese Patent No. 2635323, will be described below with reference to FIG. Here, FIG.
FIG. 1 is an explanatory plan view showing a schematic configuration of a conventional printed wiring board.

In FIG. 4, reference numeral 1 denotes a printed wiring board;
Is a front soldering land group inclined with respect to the soldering traveling direction (solder dipping direction), 3 is a rear soldering land group inclined with respect to the soldering traveling direction, and 4 is a front soldering land group 2 and rear soldering. A side solder lead-in land provided between the land group 3 and 6 is a four-way lead flat package I.
C.

In the above configuration, the side solder lead-in lands 4 each have two sides which are substantially the same width and are substantially parallel and perpendicular to the short sides of the front soldering land group 2 and one side which is parallel to the solder dip direction. The rear solder lead-in land 5 has a square shape having four sides substantially the same width and substantially parallel to the short sides of the rear soldering land group 3, respectively.

When the printed wiring board 1 on which the four-way lead flat package IC 6 is mounted is lifted out of the solder dip tank, first, the excess solder of the front soldering land group 2 is drawn off by the side solder drawing lands 4. By maintaining the surface and interfacial tension of the solder of the front soldering land group 2 and maintaining the surface and interfacial tension of the solder of the rear soldering land group 3 by the rear solder pull-in land 5, occurrence of a solder short circuit is prevented. Can be soldered.

[0007]

However, in the above-described conventional printed wiring board, it is necessary to maintain a high quality soldering without a solder short between the stable leads of a four-way lead flat package IC by a manufacturing process. Closer control is required, and the finer the pitch, the more precise the precision.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems. It is an object of the present invention to provide a printed wiring board capable of more reliably preventing the occurrence of soldering defects and preventing the occurrence of soldering defects.

[0009]

According to the present invention, there is provided a printed wiring board on which a four-way lead flat package IC is mounted, and a short side of the short side substantially matching the lead width of the four-way lead flat package IC to be soldered. A front soldering land group having lands and a rear soldering land group, and a rear soldering land formed by an enlarged rearmost land of both the rear soldering land groups, with respect to a soldering traveling direction. Between the one of the front soldering land groups tilted and the rear soldering land group facing the front soldering land group, the side soldering lands are lost, and the soldering using a jet type solder bath is performed. Thus, the four-way lead flat package IC is mounted.

In a four-way lead flat package IC having a long side and a short side, no side soldering land is provided behind a front soldering land group on the long side.
Only the front soldering land group on the short side is provided with a side soldering land formed by the enlarged rearmost land of the front soldering land group.

The enlarged and last land forming the side soldering land is formed by extending the front soldering land group as it is, and the area of each land of the four-way lead flat package IC is soldered. It has an area substantially equal to the entire area of the front soldering land.

The enlarged rearmost land of both rear soldering land groups has a shape arranged in the same direction as the soldering direction, and has an area of four-way lead flat package IC.
Has an area substantially equal to the total area of each side or the short side or the long side of the rear soldering land to which the individual leads are soldered.

In addition, except for the last land that has been enlarged,
The short side of each land on which the leads of the four-way lead flat package IC are mounted is matched with the lead width of the four-way lead flat package IC to be soldered.

Also, a four-way lead flat package I
In the area surrounded by each land group for soldering C, there is provided a linear perforated hole for preventing the adhesive for bonding the four-way lead flat package IC from flowing out.

Further, a four-way lead flat package I
In the area surrounded by each land group for soldering C
It is provided with four linear perforated holes.

That is, in the printed wiring board of the present invention, the short sides of the individual lands on which the four-way lead flat package IC is mounted are matched with the lead width of the IC to be soldered, so that each lead has a surface.・ Reducing the amount of solder that can be held by interfacial tension and maximizing the distance between the leads prevents solder shorts between the leads, and the long side of a four-way lead flat package IC consisting of a long side and a short side. Improves soldering quality by securing the distance to adjacent components by eliminating the need for soldering lands behind the front soldering land group that is the side, and increases independence by expanding the last land of each land group To prevent the occurrence of an extra solder short between the last land and the soldering land, which occurs when the soldering land is provided. The perforated hole prevents the adhesive used for temporarily fixing the four-way lead flat package IC to the printed wiring board before soldering to flow out to the lead portion of the IC to be soldered. It is possible to prevent the occurrence of additional trouble.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a printed wiring board according to the present invention will be described below with reference to FIGS. Of the reference numerals shown in the drawing, the same parts as those in the above-described conventional example are denoted by the same reference numerals, and the description thereof will be omitted. Here, FIG. 1 is a plan view showing a schematic configuration of the printed wiring board of the present embodiment, and FIG. 2 is a schematic view showing a relationship between a land of the printed wiring board of the present embodiment and a lead of a four-way lead flat package. . FIG. 3 is a schematic diagram showing the relationship between the linear perforated holes of the printed wiring board of the present embodiment and the adhesive for temporarily fixing the four-way lead flat package before soldering.

The features of the printed wiring board of the present embodiment are the differences in the shape and arrangement between the side solder drawing lands 4 and the rear solder drawing lands 5 in the conventional printed wiring board 1 described above with reference to FIG. There is a difference in the shape of each soldering land 17 in the printed wiring board 11 of the present embodiment and a difference in the presence or absence of the linear perforated hole 19.

That is, the printed wiring board 1 of the present embodiment
1, the side soldering lands 14 are arranged only at the rear end on the short side of the front soldering land group 12 as shown in FIG. 1, and the last land of the front soldering land group is enlarged to a rectangle. It is.

The rectangular area of the side soldering land 14 is equal to the area of all the soldering lands of the front soldering land group 12 located in front of the side soldering land 14.

The printed wiring board 1 according to the present embodiment
The rear soldering land 15 in FIG. 1 is obtained by expanding the rearmost land of each rear soldering land group 13 rearward in parallel with the soldering direction.

The area of each of the rearward pulling lands 15 is equal to the area of all the soldering lands of the short side land group of the rearward soldering land group 13 located in front of the rearward drawing land 15.

Next, the land width of each soldering land 17 for soldering the four-way lead flat package IC 6 on the printed wiring board 11 of the present embodiment shown in FIG.
Is the same as the width W.

Further, in the printed wiring board 11 of the present embodiment shown in FIG. 3, the adhesive 18 for temporarily fixing the four-way lead flat package IC 6 to the printed wiring board 11 before soldering flows out to the land 17 with solder. It has a linear perforated hole 19 for preventing the perforation. Linear perforated hole 19
Depending on the shape of the four-way lead flat package IC 6 and the direction in which the adhesive is applied, there may be a case where it is arranged on four sides and a case where it is arranged on two opposite sides.

Next, a description will be given of the soldering of the four-way lead flat package IC 6 using the jet solder bath on the printed wiring board 11 configured as described above. First, according to an experiment and analysis by the inventor of the present invention, 4
When the directional lead flat package IC 6 enters the solder jet portion of the jet solder bath, the solder flows rearward through the front soldering leads 20 (both front soldering lands 17) of the four-direction lead flat package IC 6. At this time,
Solder is a soldering land 17 of the front soldering land group 12,
The four-way lead flat package IC 6 moves rearward while forming bridges one after another by the action of surface and interfacial tension with the individual leads 20.

Here, by narrowing the short sides of the soldering lands 17 proposed in the present embodiment to the widths of the individual leads 20 of the four-way lead flat package IC 6, the surface and interfacial tensions are minimized to form a bridge. The amount of solder going is minimal. As a result, the effect itself reduces solder shorts, and the effect of preventing shorts in the soldering lands becomes significant.

Then, due to the surface / interfacial tension of the side soldering land 14 and the rear soldering land 15 provided at the rear end of this flow, the solder forming the bridge is sufficiently drawn in and accumulated, thereby causing a problem due to a solder short. To prevent. On the side where no side soldering land exists, narrowing of the short side of the soldering land 17 to the width of each individual lead 20 of the four-way lead flat package IC 6 is performed;
Due to the role of the rear soldering land 15, solder is applied to the surface of the solder land 17 of the front solder land group 12 and the individual leads 20 of the four-way lead flat package IC6.
While forming bridges one after another by the action of interfacial tension, they move rearward to the front soldering land group 12 and further to the opposing rear soldering land 13 and flow.

Further, the total area of the soldering lands can be reduced by reducing the width of each land. From experiments, it has been found that only the rear soldering lands 15 at the rear end of each rear soldering land group 13 can be used. Although the effect of the land 15 drawing in the solder of the land group 12 with front judgment through the rear soldering land group 13 is sufficient, the lateral soldering land 14 is provided at the rear end of the front soldering land group 12 on the short side. If so, solder short-circuit can be more reliably prevented.

When the lateral soldering land 14 provided at the rear end of the front soldering land group 12 is provided only at the rear end of the front soldering land group 12 on the long side, the short side side where the soldering land is eliminated is provided. Because the amount of solder that is maintained and moved by the surface and interfacial tension of the front soldering land group 12 is small, the solder does not fall off the land and is superimposed on the solder maintained by the rear soldering land group 13 on the long side behind. To the end.
Therefore, it is considered that the amount of solder maintained in the rear soldering land group 13 is increased, and the rear soldering land 15 may not be able to sufficiently draw in the solder of the front soldering land group 12.

On the other hand, in the case of the configuration as in the present embodiment, even if the solder maintained in the long side front soldering land group 12 is superimposed on the short side rear soldering land group 13. However, it is not maintained by the surface / interfacial tension due to a small number of lands in the rear side soldering land group 13 on the short side and falls off. Conceivable.

As described above, by providing the side soldering lands 14 only behind the front side soldering land group 12 on the long side, the solder short can be sufficiently reduced, and the other side soldering lands are eliminated. Material costs can be reduced as much as possible.

Further, it was confirmed that the soldering land was formed by enlarging the individual land at the end of each soldering land, so that the occurrence rate of the solder short could be reduced as compared with the case where the land was made independent.

The minimum area of each soldering land is the total area of the individual soldering lands 17 in the front soldering land group 12 located in front of each soldering land, and the minimum area of each rear soldering land group 13. It suffices if it is equal to the total area of the short side soldering lands 17, and the function is sufficiently exhibited.

Next, in the printed wiring board 11, 4
By providing two to four linear perforated holes 19 in the area surrounded by each land group for soldering the four-way lead flat package IC6, the four-way lead flat package IC6 is printed before soldering. It is possible to prevent the adhesive 18 temporarily fixed to 11 from flowing out to the soldering lands 17. As a result, it is possible to more reliably eliminate the problem of soldering due to the outflow of the adhesive. In addition, it also has a function of a gas vent hole for venting gas generated during soldering.

The linear perforated holes 19 may be arranged on four sides or two opposing sides depending on the shape of the four-way lead flat package IC6. May be arranged according to Also,
The size of the perforation hole 19 may be selected according to the amount of the adhesive 18 to be used.

[0036]

As described above, according to the printed wiring board of the present invention, when the four-way lead flat package IC is soldered using the jet solder bath due to surface and interfacial tension, the land is bridged. In addition to reducing the amount of solder to be moved, it is possible to more reliably prevent solder shorts while reducing the area of the soldering lands, and to reduce the number of locations where solder shorts can occur.

Further, the linear perforated hole has an effect that the outflow of the adhesive for temporarily fixing the four-way lead flat package IC is sealed, and the soldering failure due to the adhesive can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of an embodiment of a printed wiring board of the present invention.

FIG. 2 is a schematic diagram showing a relationship between a land of the printed wiring board and a lead of a four-way lead flat package in one embodiment of the printed wiring board of the present invention.

FIG. 3 is a schematic view showing a relationship between a linear perforated hole of a printed wiring board and an adhesive for temporarily fixing a four-way lead flat package before soldering in an embodiment of the printed wiring board of the present invention. is there.

FIG. 4 is a plan view showing a schematic configuration of a conventional printed wiring board.

[Explanation of symbols]

6 4-way lead flat package, 11 printed wiring board, 12 front soldering land group, 13 rear soldering land group, 14 side soldering land, 15
Rear soldering land, 17 Soldering land, 18
Glue, 19 drilled holes, 20 leads.

Continued on the front page F term (reference) 4E080 AA01 AB03 DA04 5E319 AA01 AB03 AC12 AC15 CC24 GG05 5F067 AB03

Claims (7)

[Claims] 1. A front soldering land group and a rear soldering land on which a four-way lead flat package IC is mounted and which has a land on a short side substantially matching a lead width of the four-way lead flat package IC to be soldered. Group, and a rear soldering land formed by the enlarged rearmost land of both the rear soldering land groups, and one of the front soldering land groups inclined with respect to the soldering traveling direction. The four-way lead flat package IC is mounted between the front soldering land group and the rear soldering land group facing the rear soldering land group, while deficient in the side soldering land and by soldering using a jet type solder bath. A printed wiring board, characterized in that: 2. The printed wiring board according to claim 1, wherein in a four-way lead flat package IC having a long side and a short side, a side soldering land is provided behind the front soldering land group on the long side. A printed wiring board characterized in that a side soldering land formed by an enlarged rearmost land of the front soldering land group is provided only in the front soldering land group on the short side side without providing . 3. The printed wiring board according to claim 2, wherein the enlarged last land forming the side soldering land has a shape in which the front soldering land group is extended as it is, and has an area of four-way lead flat. A printed wiring board having an area substantially equal to the entire area of a front soldering land to which individual leads of a package IC are soldered. 4. The printed wiring board according to claim 1, wherein the enlarged rearmost land of both rear soldering land groups has a shape arranged in the same direction as the soldering direction. A printed wiring board having substantially the same area as the entire area of each side or short side or long side of a rear soldering land to which individual leads of a four-way lead flat package IC are soldered. 5. The printed wiring board according to claim 1, wherein a short side of each land on which the lead of the four-way lead flat package IC is mounted is removed, except for the enlarged last land. A printed wiring board characterized by having a lead width to be soldered. 6. A linear perforated hole for preventing the outflow of an adhesive for bonding the four-way lead flat package IC in a range surrounded by each land group for soldering the four-way lead flat package IC. A printed wiring board, comprising: 7. The printed wiring board according to claim 6, wherein two to four linear perforated holes are provided in a range surrounded by each land group for soldering the four-way lead flat package IC. A printed wiring board, characterized in that: