JP2000040869A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a solder bridge even if a four-way flat package IC is mounted on a printed wiring board and this printed wiring board is soldered by solder dip method. SOLUTION: A frontward soldering land group 3 and a rearward soldering land group 4 are made, corresponding to each lead 2a and 2a' of a flat package IC2. Sideward solder drawing lands 5 and 6 are made between the frontward soldering land groups 3 and 3 and the rearward soldering land groups 4 and 4, and a lead 2a which serves as a tail in the direction of the progress of the above soldering of the frontward lead group of the flat package IC2 is arranged, and also the flow S of solder is drawn from the frontward solder land groups 3 and 3 to the rearward soldering land groups 4 and 4. First rearward solder drawing lands 7 and 8 are made between several rearward soldering land group 4 and 4, and a lead 2a' which serves as a tail in the direction of the progress of the above soldering of the rearward lead group of the flat package IC2 is arranged, and the flow S of solder is drawn rearward in the direction of the progress of the above soldering from each rearward soldering land groups 4 and 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board on which a four-way flat package IC is mounted inclined with respect to the direction of soldering, and more particularly to a printed wiring board on which the flat package IC is soldered by a solder dip method. It is about a board.

[0002]

2. Description of the Related Art In a printed wiring board for soldering a four-way flat package IC, a solder bridge is provided between the solder lands and between the leads with respect to the solder lands of the printed wiring board and the leads of the flat package IC. In order to prevent the occurrence of short circuits and the occurrence of short circuit defects, there has been proposed a printed wiring board in which the flat package IC is mounted at an angle with respect to the direction of soldering.
Regarding the above contents, for example, Japanese Patent Application Laid-Open No. 63-213994 has been proposed.

[0003] This printed wiring board corresponds to a four-way flat package IC on the printed wiring board, and forms a front soldering land group and a rear soldering land group inclined with respect to the direction of soldering. A substantially triangular side soldering land formed between the attached land group and the rear soldered land group improves the flow of solder, and a substantially triangular shape larger than each land is formed between each rear soldered land group. By providing the rear soldering lands to be formed, the solder bridge is prevented by the rear soldering lands larger than each land without changing each land.

[0004] The leads of the flat package IC are disposed so as to correspond to the front solder land group and the rear solder land group formed on the printed wiring board, and the flat package IC is mounted on the printed wiring board.
Is soldered by a solder dip tank in a state where the flat package IC is tilted with respect to the direction of the soldering (solder dipping method), so that short circuit failure is reduced as compared with a case where the flat package IC is not tilted.

[0005]

However, even when the above-mentioned printed wiring board is used, various conditions such as solder temperature, solder flow rate, flux component, and solder component in the solder dip tank are not considered. Differences between the lands of the respective land groups and of the flat package IC due to differences in mounting of the respective leads of the flat package IC with respect to the respective soldered land groups when the flat package IC is mounted by an automatic mounting machine or the like. A short circuit occurs between the leads due to a solder bridge. Therefore,
In a printed wiring board in which a four-way flat package IC is soldered by a solder dip method, a printed wiring board which can prevent the occurrence of a solder bridge and achieve stable quality is required.

Accordingly, the present invention focuses on the above problems, and
An object of the present invention is to provide a printed wiring board that can prevent the occurrence of a solder bridge even when a directional flat package IC is mounted on a printed wiring board and the printed wiring board is soldered by a solder dipping method.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a four-lead structure including a front lead group and a rear lead group.
A printed wiring board on which a flat package IC is mounted obliquely with respect to the direction of soldering, comprising a front solder land group and a rear solder land group formed corresponding to each lead group of the flat package IC. And a lead formed between the front soldering land group and the rear soldering land group and arranged rearward in the soldering progression direction of the front lead group of the flat package IC. A side soldering land for drawing a flow from the front soldering land group to the rear soldering land group, and the soldering progress of the rear lead group of the flat package IC formed between the rear soldering land groups. A lead that is the tail in the direction is provided, and the flow of the solder is drawn rearward from the rear soldering land group in the soldering direction. And the rear solder drawing land, is intended to be constructed from.

A printed wiring board on which a four-way flat package IC having a front lead group and a rear lead group is mounted while being inclined with respect to the direction of soldering, and corresponds to each lead group of the flat package IC. A front soldering land group and a rear soldering land group formed between the front soldering land group and the rear soldering land group, and the solder of the front lead group of the flat package IC. A rear lead is disposed in the direction of the soldering, and a side soldering land for drawing the flow of solder from the front soldering land group to the rear soldering land group, and between the rear soldering land groups. A lead, which is formed and is located at the end of the rear lead group of the flat package IC with respect to the soldering direction, is disposed, and the flow of the solder is set at the front. A first rear soldering land that is pulled rearward from the rear soldering land group with respect to the soldering traveling direction; and a second rear soldering land formed at a position rearward of the first rear soldering land with respect to the soldering traveling direction. And a rear soldering land.

A printed wiring board on which a four-way flat package IC having a front lead group and a rear lead group is mounted while being inclined with respect to the direction of soldering, corresponding to each lead group of the flat package IC. A front soldering land group and a rear soldering land group formed between the front soldering land group and the rear soldering land group, and the solder of the front lead group of the flat package IC. A rear lead is disposed in the direction of the soldering, and a side soldering land for drawing the flow of solder from the front soldering land group to the rear soldering land group, and between the rear soldering land groups. A lead, which is formed and is located at the end of the rear lead group of the flat package IC with respect to the soldering direction, is disposed, and the flow of the solder is set at the front. A first rear soldering land that is pulled rearward in the soldering direction from the rear soldering land group, and a land of the rear soldering land group adjacent to the first rear soldering land are formed integrally. With
A second rear soldering land which is larger than the first rear soldering land and at least a portion of which is formed at a position rearward of the first rear soldering land with respect to the soldering direction. Things.

[0010] The side soldering lands are formed in a substantially arc shape.

A constriction is formed between the first rear soldering land and the second rear soldering land.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a printed wiring board on which a four-way flat package IC is mounted at an angle with respect to the direction of soldering. The printed wiring board 1
A front soldering land group 3 and a rear soldering land group 4 corresponding to the leads 2a and 2a 'of the front and rear lead groups of the flat package IC 2 are formed, and the front soldering land groups 3 and 3 and the rear soldering are formed. Between the land groups 4 and 4, a lead 2a which is the tail of the front lead group of the flat package IC 2 with respect to the soldering traveling direction is disposed, and the flow S of the solder is set to each of the front solder land groups 3 and 4. 3 is provided with lateral soldering lands 5 and 6 for drawing from the rear to each rear soldering land group 4 and 4. The printed wiring board 1 has a flat package IC 2 between the rear soldering land groups 4 and 4.
Of the rear lead group of the rear lead group is disposed rearward in the soldering traveling direction, and the flow S of the solder is pulled backward from the rear soldering land groups 4 and 4 in the soldering traveling direction. First rear soldering lands (rear soldering lands) 7 and 8 are provided.

In each of the side soldering lands 5 and 6 of the printed wiring board 1, the leads 2a of the flat package IC 2 are disposed on the flat soldering lands. Therefore, the flow S of the solder can be satisfactorily pulled by the side soldering lands 5, 6 and the rear soldering land groups 4, 4. Also, in each of the first rear soldering land groups 7 and 8, each side soldering land 5,
6, the lead 2a 'is disposed on the flat soldering land, so that the surface tension is increased by the amount of the lead 2a' as compared with the prior art.
Can be satisfactorily pulled by the first rear soldering lands 7 and 8. Therefore, even if the solder conditions in the solder bath are different or the flat package IC 2 is mounted shifted from each of the land groups 3 and 4, each of the front soldering land groups 3 and 3 and each of the rear soldering lands. It is possible to prevent the occurrence of a solder bridge between the lands and the leads near the rear end of the groups 4 and 4 and the front and rear leads of the flat package IC 2 in the soldering direction.

Further, according to the present invention, the second rear soldering lands 9, 10 are formed at positions rearward of the first rear soldering lands 7, 8 with respect to the soldering traveling direction. Therefore, the first
The solder pulled rearward by the rear soldering lands 7, 8 is pulled further rearward by the second rear soldering lands, so that each rear soldering land group 4, 4 and each rear lead of the flat package IC2 are formed. It is possible to prevent the occurrence of a solder bridge between the lands and between the leads near the rear end in the soldering traveling direction of the group.

According to the present invention, the second rear soldering lands 13 and 14 are formed integrally with the lands 4a of the rear soldering land groups 4 and 4 adjacent to the first rear soldering lands 7 and 8, respectively. And the second rear soldering land 1 is larger than the first rear soldering lands 7 and 8 and
The portions 3 and 14 are formed so as to be located behind the first rear soldering lands 7 and 8. Therefore,
Since the solder pulled rearward by the first rear soldering lands 7, 8 is further pulled rearward by the second rear soldering lands, each of the rear soldering land groups 4, 4 and the flat package IC2 has It is possible to prevent the occurrence of a solder bridge between the lands and between the leads near the rear end in the soldering direction of the rear lead group.

Each of the first rear soldering lands 7, 8
When the second rear soldering lands 9 and 10 are formed integrally with each other, each first rear soldering land 7 and 8 and each second rear soldering land 9 and 10 , 8, 9, 10 are connected via the constrictions 11, 12, which are narrower than the second rear soldering lands 9, 10, and are connected to the second rear soldering lands 9, 10, respectively.
The excess solder accumulated in the first and second rear soldering lands 4 and 4 and the flat package IC 2 is prevented from returning to the first rear soldering lands 7 and 8 by the narrow constrictions 11 and 12. It is possible to prevent the occurrence of a solder bridge between the lands and between the leads near the rear end in the soldering progress direction of each rear lead group.

Further, since the shape of each of the side soldering lands 5 and 6 is formed in a substantially arc shape, a land is not formed near the corner portion of the flat package IC 2 as in the conventional case, so that the flow S of the solder flows forward. It is possible to smoothly flow from the soldering land groups 3, 3 to the rear soldering land groups 4, 4.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the accompanying drawings. FIG. 1 is a view showing a solder dip land on a printed wiring board for soldering a four-way flat package IC by a solder dip method according to a first embodiment of the present invention, and FIG. 2 is a view showing a printed wiring board according to the first embodiment. FIG. 3 is a view showing a flow S of soldering when the flat package IC is mounted and soldering is performed by a solder dip method, FIG. 3 is an enlarged view of a main part of a solder dip land, and FIG. 4 is a second embodiment of the present invention. FIG. 5 is a view showing a solder dip land on a printed wiring board. FIG. 5 is a view showing a flow S of solder when the flat package IC is mounted on the printed wiring board in the second embodiment and soldering is performed by a solder dip method. It is.

A first embodiment of the present invention will be described with reference to FIGS. In the drawing, reference numeral 1 denotes a printed wiring board made of paper phenol or a resin containing glass fiber, etc., 2 denotes a four-way flat package IC, and 3 and 4 denote solder dip lands on which the flat package IC 2 is mounted. The flat package IC2 is inclined such that one corner is at the top in the soldering direction (DIP direction) and the other corner opposite to the corner is at the tail in the soldering direction. Flat package IC2 formed
And a front soldering land group and a rear soldering land group corresponding to each front lead group and each rear lead group. 5,6
Is formed between each of the front soldering land groups 3 and 3 and each of the rear soldering land groups 4 and 4, and transfers the solder flow S by the solder dip method from the front soldering land group 3 to the rear soldering land group 4. In order to make the lands flow smoothly, the fan-shaped lands are cut out in a substantially arc shape at a portion located near the corner of the flat package IC2, and the lands themselves are formed in a substantially arc shape. Further, reference numerals 7 and 8 are formed between the rear soldering land groups 4 and 4, respectively, to form a flat package IC.
2 is a pair of first rear soldering lands formed in the vicinity of a corner which is the rear end in the soldering traveling direction. 9,
Numeral 10 denotes second rear soldering lands formed integrally with the first rear soldering lands 7 and 8, respectively.
The rear soldering lands 9 and 10 of each of the first and second rear soldering lands 9 and 1 and the second rear soldering lands 9 and 1 respectively.
It is formed integrally with each of the first rear soldering lands 7 and 8 via narrow portions 11 and 12 which are narrower than zero.

Each of the side soldering lands 5 and 6 has an effect of favorably flowing the flow S of the solder by the solder dipping method from the front soldering land group 3 to the rear soldering land group 4.
It is also a land for soldering the lead 2a located at the rear end of the front lead group of the flat package IC 2 in the solder advancing direction. The first rear soldering lands 7 and 8 serve to pull the flow S of the solder by the solder dipping method backward in the soldering progression direction, and also to advance the solder of the rear lead group of the flat package IC2. It is also a land for soldering the lead 2a 'located at the rear end in the direction.

Therefore, in the first embodiment, each of the side soldering lands 5, 6 and each of the first rear soldering lands 7,
8 is characterized in that it also serves as a land for soldering the leads 2a and 2a 'of the front lead group and the rear lead group of the flat package IC2.

Here, a flat package I is provided for each of the front soldering land groups 3, 3 and the rear soldering land groups 4, 4.
A description will be given of a case where the leads 2a and 2a 'of C2 are mounted in a shifted state, and are directly soldered by a solder dipping method. FIG. 3 is an enlarged plan view of the front soldering land groups 3 and 3 in the vicinity of the side soldering lands 5 and 6.

When the flat package IC 2 is mounted by an automatic mounting machine, the mounting accuracy in the automatic mounting machine and the accuracy of the printed wiring board 1 itself (shifts when positioning the automatic mounting machine, shifts in land layout, etc.). Each land 3 of the front and rear soldering land groups 3 and 4
a, 4a to lead 2 of flat package IC2
a and 2a 'are mounted in a shifted state. In FIG. 3, the distance W1 between the end of the land 3a of the front soldering land group 3 and the end of the lead 2a is equal to the distance W between the lands 3a.
2 (W1 <W2), so that a solder bridge easily occurs between lands and between leads.

In the conventional printed wiring board, each side solder soldering land formed between each front soldering land group and each rear soldering land group causes the flow S of solder to flow toward the rear soldering land group. When trying to pull the solder, the surface tension is insufficient due to the flat soldering land, and the solder cannot be pulled to the rear soldering land group. Solder bridges occur between lands and between leads near the rear end.

On the other hand, each side soldering land 5, 6 of the printed wiring board 1 in this embodiment is provided with a lead 2 a of the flat package IC 2 on a flat soldering land.
Is provided, the surface tension is increased in the lead 2a compared with the conventional case, so that the flow S of the solder is controlled by the side soldering lands 5, 6 and the rear soldering land groups 4, 4. It is possible to satisfactorily pull and prevent the occurrence of solder bridges between lands and leads near the rear end in the soldering progression direction of the front soldering land groups 3 and 3 and each front lead of the flat package IC 2. Can be done.

The same applies to the first rear soldering lands 7 and 8 as described above. That is, each of the rear soldering lands 7 and 8 is connected to each of the side soldering lands 5 and 6.
Since the leads 2a 'are disposed on the flat soldering lands in the same manner as described above, the surface tension is increased by the amount of the leads 2a' as compared with the prior art. The rear soldering lands 7 and 8 enable good pulling.

Each of the first rear soldering lands 7, 8
Is provided with the second rear soldering lands 9 and 10 connected via the constrictions 11 and 12, respectively, so that the flow S of the solder flows through the first rear soldering lands 7 and 12.
8 and are further pulled rearward by the second rear soldering lands 9 and 10 located behind the first rear soldering lands 7 and 8 with respect to the soldering direction. Further, the solder drawn on the second rear soldering lands 9 and 10 becomes excess solder and accumulates on the second rear soldering lands 9 and 10, but the excess solder has a narrow width. The constrictions 11 and 12 suppress the return to the first rear soldering lands 7 and 8. Accordingly, in the printed wiring board 1, since a double soldering structure is obtained at the rear of the flat package IC2 in the soldering direction, the rear soldering land groups 4 and 4 and the rear of the flat package IC2. It is possible to prevent the occurrence of a solder bridge between the lands and between the leads near the rear end in the soldering direction of the lead group.

Next, a second embodiment of the present invention will be described with reference to FIG. 4, but the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The difference between the printed wiring board 1 of the second embodiment and the printed wiring board 1 of the first embodiment is that the first rear soldering lands 7 and 8 have constricted portions 11 and 12 respectively.
Instead of integrally forming the second rear soldering lands 9, 10 through the respective first rear soldering lands 7, 8.
Each land 2 of each rear soldering land group 4, 4 adjacent to
a'2a ', the second rear soldering lands 13, 14
It is in the point with. Each second rear soldering land 13,
14 is formed integrally with each land 2a'2a 'of each rear soldering land group 4, 4 adjacent to each first rear soldering land 7, 8, and each first rear soldering land 7 , 8 and a portion thereof is formed so as to extend so as to be located behind each of the first rear soldering lands 7, 8 in the solder advancing direction, and to extend from the first rear soldering lands 7, 8. It is formed on a land having a large area.
The side soldering lands 5, 6 and the rear soldering lands 7, 8 are flat package I as in the first embodiment.
It also serves as a soldering land for the leads 2a and 2a 'of C2.

The printed wiring board 1 having such a configuration is mounted so that the leads 2a and 2a 'of the flat purge IC 2 correspond to the front soldering lands 3 and 3 and the rear soldering lands 4 and 4 by a solder dipping method. When the soldering is performed, the flow S of the solder is favorably transferred from the front soldering land groups 3, 3 to the rear soldering land groups 4, 4 by the side soldering lands 5, 6 as in the first embodiment. Each of the first rear soldering lands 7 and 8 has a larger area than each of the first rear soldering lands 7 and 8. By the second rear soldering lands 13 and 14 having a large surface tension located behind the first rear soldering lands 7 and 8,
You will be pulled further back. Therefore, in the printed wiring board 1, a double soldering structure is obtained at the rear part of the flat package IC 2 in the soldering direction in the same manner as in the first embodiment.

Each of the first rear soldering lands 7, 8
Second rear soldering lands 1 having a greater surface tension than
The solder pulled rearward by the third and third rear soldering lands 13 and 14 accumulates as excess solder on the second rear soldering lands 13 and 14, respectively. Since the resist film (not shown) of the printed wiring board 1 exists between the second rear soldering lands 13 and 14 and the surface tension of the first rear soldering lands 7 and 8 is small, Return to the first rear soldering lands 7 and 8 is suppressed, so that the rear soldering lands 4 and 4 and the rear lead group of the flat package IC 2 are in the vicinity of the rear end in the soldering advancing direction. This can prevent the occurrence of solder bridges between lands and leads.

In each of the above-described embodiments, the shape of each of the side soldering lands 5 and 6 is formed in a substantially circular arc shape. This is because the flow S of the solder flows smoothly from the front soldering land groups 3, 3 to the rear soldering land groups 4, 4.

The substantially arc-shaped side soldering lands 5, 6
Is a substantially arc shape having a width substantially equal to the longitudinal width of a joint portion between each of the front and rear soldering land groups 3 and 4 and the front and rear lead groups of the flat package IC 2;
It is desirable to set the width of the rear soldering land groups 3 and 4 in a substantially arc shape having a width substantially equal to the width in the longitudinal direction, and it is desirable to appropriately change the layout according to layout conditions of other electronic components of the printed wiring board 1.

The shapes of the first and second rear soldering lands in the present invention are not limited to those of the present embodiment. Can be changed.

Further, the rear ends of the second rear soldering lands 13 and 14 in the second embodiment with respect to the soldering direction are
You may make it form the 3rd solder pull land connected via a constriction part.

Also, in the present embodiment, the second rear soldering lands 9, 10, 13, 14 are formed on the lands 4a of the rear soldering land groups 4, 4 on both sides. In consideration of the mounting layout of other electronic components,
It may be provided on the rear soldering land group 4 on one side.

In each of the above-described embodiments, the first rear soldering lands 7, 8 and the second rear soldering lands 9,
In the present invention, the second rear soldering lands 9, 10, 13, and 14 are formed.
14, the solder may be pulled backward only by the rear soldering land with respect to the soldering traveling direction. Even in this case, the solder flow may be used as the connection land of the flat package IC2. Can be favorably pulled.

[0038]

The present invention provides a four-way flat package I.
C relates to a printed wiring board in which the flat package IC is soldered by a solder dipping method and is mounted at an angle with respect to the soldering proceeding direction. , 4, even if implemented
By satisfactorily flowing the flow of the solder by the solder dip method behind the flat package IC, it is possible to provide a printed wiring board that does not generate a solder bridge.

[Brief description of the drawings]

FIG. 1 is a plan view showing a solder dip land of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a view showing a state in which a flat package IC is mounted on the printed wiring board in the first embodiment.

FIG. 3 is a diagram showing a mounting state of the flat package IC.

FIG. 4 is a plan view showing a solder dip land of a printed wiring board according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a state in which a flat package IC is mounted on a printed wiring board in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Flat package IC 2a, 2a 'Lead 3 Front soldering land group 3a Land 4 Rear soldering land group 4a Land 5, 6 Side soldering land 7, 8 First rear soldering land 9, 10 Second rear soldering land 11, 12 Narrow portion 13, 14 Second rear soldering land S Solder flow

Claims (5)

[Claims] 1. A printed wiring board on which a four-way flat package IC having a front lead group and a rear lead group is mounted at an angle with respect to a soldering direction, and corresponds to each lead group of the flat package IC. And a front soldering land group and a rear soldering land group formed between the front soldering land group and the rear soldering land group, and the solder of the front lead group of the flat package IC. Along with a lead that is a trailing end in the soldering direction, a side soldering land for drawing the flow of solder from the front soldering land group to the rear soldering land group, and between the rear soldering land groups. A lead formed in the rear package group of the flat package IC and arranged rearward in the soldering direction is disposed, and the flow of the solder is And a rear soldering land which is pulled rearward in the soldering direction from the soldering land group. 2. A printed wiring board on which a four-way flat package IC having a front lead group and a rear lead group is mounted while being inclined with respect to the direction of soldering, corresponding to each lead group of the flat package IC. And a front soldering land group and a rear soldering land group formed between the front soldering land group and the rear soldering land group, and the solder of the front lead group of the flat package IC. Along with a lead that is a trailing end in the soldering direction, a side soldering land for drawing the flow of solder from the front soldering land group to the rear soldering land group, and between the rear soldering land groups. A lead formed in the rear package group of the flat package IC and arranged rearward in the soldering direction is disposed, and the flow of the solder is A first rear soldering land which is pulled rearward in the soldering traveling direction from the soldering land group, and a second rear formed at a position rearward of the first rear soldering land in the soldering traveling direction. A printed wiring board comprising: a soldering land; 3. A printed wiring board on which a four-way flat package IC having a front lead group and a rear lead group is mounted while being inclined with respect to the direction of soldering, corresponding to each lead group of the flat package IC. And a front soldering land group and a rear soldering land group formed between the front soldering land group and the rear soldering land group, and the solder of the front lead group of the flat package IC. Along with a lead that is a trailing end in the soldering direction, a side soldering land for drawing the flow of solder from the front soldering land group to the rear soldering land group, and between the rear soldering land groups. A lead formed in the rear package group of the flat package IC and arranged rearward in the soldering direction is disposed, and the flow of the solder is A first rear soldering land that is pulled rearward in the soldering direction from the one soldering land group; and a land of the rear soldering land group adjacent to the first rear soldering land. A second rear soldering land which is larger than the first rear soldering land and at least a part of which is formed at a position rearward of the first rear soldering land in the soldering direction. A printed wiring board characterized by being constituted. 4. The method according to claim 1, wherein the side soldering lands are formed in a substantially arc shape.
The printed wiring board according to any one of the above. 5. The printed wiring board according to claim 2, wherein a constricted portion is formed between the first rear soldering land and the second rear soldering land.