JP2925376B2 - Circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board on which electronic components such as semiconductor devices are surface-mounted.

[0002]

2. Description of the Related Art As is well known, in recent years, smaller and higher-performance computers and various industrial equipment have been demanded. As a result, electronic components such as semiconductor devices have become smaller and more integrated, and a circuit board on which the electronic components are mounted is required to be compatible with them.

Hereinafter, a conventional circuit board will be described with reference to FIG. FIG. 5 is a cross-sectional view. The circuit board 1 has a circuit 3 of a predetermined pattern formed by a conductive foil such as a copper foil on an upper surface of a board 2 formed of an insulating material. The electronic component, for example, the semiconductor device 4 is provided with a plurality of lead terminals 5 formed in the gull-wing shape by a corresponding circuit 3
Is mounted on the circuit board 1 by soldering to the land 6.

The soldering surface 8 of the land 6 to which the end 7 of the lead terminal 5 is soldered is formed parallel to the surface of the substrate 2, that is, at a uniform height. The end portion 7 of the lead terminal 5 formed in parallel with this surface comes into contact with 8, and is fixed to the contact portion with a solder 9 interposed therebetween.

[0005] However, in the above prior art,
In the integrated and miniaturized semiconductor device 4, the terminal width is small, and the end 7 of the lead terminal 5 is parallel to the soldering surface 8. And the amount of the solder 9 interposed between them was small, and the fixing strength could not be increased. When the semiconductor device 4 to be mounted is more highly integrated and the number of lead terminals 5 is large, for example, in a QFP (Quad Flat Package), the cross-sectional dimension is 0.2 mm square or 0.1 mm × 0.2 mm.
A large number of lead terminals 5 are provided at an arrangement interval of 0.4 mm to 0.5 mm. Since the amount of solder 9 cannot be interposed, it is difficult to secure a fillet portion of the solder 9 at the tip of the lead terminal 5, and there is a possibility that the lead terminal 5 cannot be securely fixed to the soldering surface 8. .

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the situation where conventional lead terminals having a narrow lead terminal width cannot provide a sufficient fixing strength. To provide a circuit board that can be mounted with sufficient bonding strength even in the situation where the brazing part becomes finer when mounting, and that can respond to the demand for miniaturization and high functionality of computers and various equipment. is there.

[0007]

The circuit board of the present invention comprises a plurality of circuit boards.
Insulating material on which electronic components having a number of lead terminals are mounted
Circuit board with a substrate made of
Has a land for brazing the end of the lead terminal.
And the brazing surface of the land is
High and low surfaces that differ in height in the direction in which the ends of the
And the end of the lead terminal was brazed to the land
When the tip of the end of the lead terminal is located above the low surface portion,
A gap corresponding to the difference in height between the high surface portion and the low surface portion
Between the distal end of the lead terminal end and the low surface of the land.
Formed so that the voids are filled with brazing material
And characterized in that it is further run
The brazing surface, which has a high side and a low side, is
It is characterized by an inclined surface consisting of an inclined plane
There further wax having a high surface and a low surface of the land portion
The mounting surface is inclined with a flat surface and a monotonically lower surface.
Characterized by an inclined plane with an inclined plane
It is.

[0008]

In the circuit board constructed as described above, the brazing surface of the land for brazing the lead terminal of the electronic component is adjusted so that the height of the portion corresponding to the tip of the lead terminal is reduced. Thus, when the brazed portion of the lead terminal comes into contact with the brazing surface of the land portion, a gap is formed between the two at the tip end side of the lead terminal. Then, an appropriate amount of brazing material is interposed in the gap when brazing, and a fillet portion is formed at the tip of the lead terminal. Therefore, the electronic component can be mounted so that the brazed portion has sufficient reliability and fixing strength.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment will be described with reference to FIGS. 1 is a perspective view, FIG. 2 is a sectional view,
In the figure, a circuit board 11 is formed of an insulating material such as a phenol resin or an epoxy resin. A conductive foil such as a copper foil is adhered to an upper surface of a board 12, and a circuit 13 having a predetermined pattern is formed by etching the conductive foil. It is configured. The circuit 1 formed on the upper surface of the substrate 12
3 is formed with a land portion 14 for surface mounting the corresponding lead terminal of the electronic component on the circuit board 11 by brazing with a brazing material, for example, solder.
The upper surface 4 of the brazing surface 15 is divided into two stages of height, high and low, and is formed to have a high surface portion 15a and a low surface portion 15b. The low surface portion 15b is adapted to correspond to the tip end side of the lead terminal of the electronic component to be mounted. Also, the brazing surfaces 15 having different heights of the land portions 14 are provided.
Is formed by mechanically shaving the low surface portion 15b after the high surface portion 15a is formed, by performing etching again, or by forming the electroless copper plating or copper foil after forming the low surface portion 15b. This is performed by forming a high surface portion 15a by bonding.

The circuit board 1 constructed as described above
The mounting of the electronic component, for example, the semiconductor device 16 on the semiconductor device 1 is performed as follows. The semiconductor device 16 has a package 17 containing a semiconductor chip and a number of lead terminals 18 connected to the semiconductor chip and extending outside the package 17. The lead terminal 18 is formed in a gull-wing shape. The ends 19 to be attached to the circuit board 11 are formed and arranged so as to form a flat surface.

That is, prior to mounting of the semiconductor device 16, a thin film of the solder 20 is fused to the brazing surface 15 of the land portion 14, and then the semiconductor device 16 is placed at the mounting position of the circuit 13. . At this time, the many lead terminals 18 of the semiconductor device 16 are arranged such that the end portions 19 are located on the brazing surfaces 15 of the corresponding land portions 14. Further, at this time, the lead terminal 18 is configured such that the portion of the end portion 19 on the package 17 side contacts the thin film of the solder 20 on the high surface portion 15a, and the front end side is located on the low surface portion 15b side. As a result, the height difference between the high surface portion 15a and the low surface portion 15b between the front end portion of the end portion 19 and the low surface portion 15b of the brazing surface 15 (this height difference is, for example, the height of the lead terminal 18) 1 /
It is formed in about 2/3. ) Is generated. Then, the solder 20 is melted, and the end 19 of the lead terminal 18 is brazed to the brazing surface 15 of the corresponding land 14.

As a result, the gap between the front end portion of the end portion 19 of the lead terminal 18 and the low surface portion 15b of the brazing surface 15 is filled with the solder 20, and even if the terminal width is small, the end portion 1 is small.
9 is provided with a fillet portion at the leading end, and lead terminals 1
Even when the wires 8 are provided at a narrow pitch, there is no bridge and no short circuit occurs between the terminals, and the end 19 of the lead terminal 18 and the brazing surface 15 are brazed with an appropriate amount of solder 20 interposed therebetween.

Thus, the lead terminals 18 are connected to the brazing surface 1.
5, and absorbs thermal stress in the direction parallel to the extending direction of the end portion 19 of the lead terminal 18 acting on the brazing portion even in the semiconductor device 16 in which the width of the lead terminal 18 is particularly small. With sufficient bonding strength,
Further, it can be mounted on the circuit board 11 with high mechanical reliability. And it can contribute to realization of miniaturization and high functionality of computers and various devices.

Next, a second embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view. In the figure, a circuit board 21 has a land portion 22 for brazing an electronic component to a circuit 13 formed on the upper surface of the substrate 12 and surface mounting the same. The land portion 22 is a flat surface in which the brazing surface 23 on the upper surface is monotonously inclined. The inclination of the brazing surface 23 is such that the height of the brazing surface 23 decreases toward the tip end side of the lead terminal of the electronic component to be mounted.

The circuit board 2 constructed as described above
In mounting the electronic component, for example, the semiconductor device 16, a thin film of the solder 20 is first fused to the brazing surface 23 of the land 22 in the same manner as in the first embodiment. Place on the mounting position. At that time, the semiconductor device 1
The six lead terminals 18 are arranged such that the ends 19 are located on the brazing surfaces 23 of the corresponding lands 22. Further, at this time, the lead terminal 18 has a part of the end portion 19 on the package 17 side in contact with the thin film of the solder 20 on the higher inclined surface, and the leading end is positioned on the lower inclined surface. As a result, a wedge-shaped gap is formed between the portion of the end portion 19 from the portion in contact with the thin film of the solder 20 to the tip portion and the inclined brazing surface 23. Then, the solder 20 is melted and the end 19 of the lead terminal 18 is brazed to the brazing surface 23 of the corresponding land 22.

As a result, the wedge-shaped space between the end portion 19 of the end portion 19 of the lead terminal 18 and the brazing surface 23 is filled with the solder 20, and even if the terminal width is narrow, the end portion of the end portion 19 is small. Lead terminals 18
End 19 and brazing surface 23 are brazed with an appropriate amount of solder 20 interposed therebetween.

In this embodiment, the same operation and effect as those of the first embodiment can be obtained.

Next, a third embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view. In the figure, a circuit board 31 has a land portion 32 for soldering an electronic component to a circuit 13 formed on the upper surface of the board 12 and surface mounting the same. The land portion 32 has a brazing surface 33 on the top surface which is a flat portion 33a.
And a flat inclined surface portion 33b inclined so as to be monotonously lowered from the flat surface portion 33a. The height of the inclined surface portion 33b of the brazing surface 33 decreases toward the tip end of the lead terminal of the electronic component to be mounted.

The circuit board 3 constructed as described above
In mounting the electronic component, for example, the semiconductor device 16, a thin film of the solder 20 is first fused to the brazing surface 33 of the land 32 in the same manner as in the first embodiment. Place on the mounting position. At that time, the semiconductor device 1
6 are arranged so that the end portions 19 are located on the brazing surfaces 33 of the corresponding land portions 32. At this time, the lead terminal 18 has a portion of the end 19 on the package 17 side in contact with the thin film of the solder 20 on the flat portion 33a, and the tip end is positioned on the inclined surface portion 33b. As a result, a wedge-shaped gap is formed between the tip end portion of the end portion 19 and the inclined surface portion 33b. Then, the solder 20 is melted and the end 19 of the lead terminal 18 is brazed to the brazing surface 33 of the corresponding land 32.

As a result, the wedge-shaped space between the end portion 19 of the end portion 19 of the lead terminal 18 and the brazing surface 33 is filled with the solder 20, and even if the terminal width is small, the end portion of the end portion 19 is small. Lead terminals 18
End 19 and brazing surface 33 are brazed with an appropriate amount of solder 20 interposed therebetween.

In this embodiment, the same operation and effect as those of the first embodiment can be obtained.

It should be noted that the present invention is not limited to only the above embodiments, but can be implemented with appropriate modifications without departing from the scope of the present invention.

[0024]

As is apparent from the above description, according to the present invention, the brazing surface of the land portion for brazing the lead terminal of the electronic component has the height corresponding to the tip of the lead terminal. By configuring so as to be lower, the mounting of electronic components can be performed with sufficient reliability and bonding strength even in the situation where the brazed part is finer, and furthermore, such as equipment to which the mounted one is mounted This has the effect of being able to meet demands for downsizing and higher functionality.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the first embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of a second embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of a third embodiment of the present invention.

FIG. 5 is a sectional view showing a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Board 14 ... Land part 15 ... Brazing surface 15a ... High surface part 15b ... Low surface part 16 ... Semiconductor device 18 ... Lead terminal 19 ... End part 20 ... Solder

Claims (3)

(57) [Claims] An electronic component having a plurality of lead terminals is realized.
Circuit board with a board made of insulating material
The end of the lead terminal is soldered to one main surface of the substrate.
And a land portion for attaching the
The brazing surface of the lead portion extends in the direction in which the end of the lead terminal extends.
The lead terminal having a high surface portion and a low surface portion having different heights,
When the end of the lead terminal is brazed to the land,
The tip of the end is located above the low surface, and the high surface
A gap corresponding to the difference in height between the lead terminal and the lower surface
Formed between the tip side portion of the portion and the low surface portion of the land portion
Is formed so that the void is filled with the brazing material.
A circuit board, comprising: 2. A land having a high surface portion and a low surface portion.
The mounting surface must be a monotonically inclined plane.
The circuit board according to claim 1, wherein: 3. A land having a high surface portion and a low surface portion.
The mounting surface is inclined with a flat surface and a monotonically lower surface.
And a slanted flat surface.
Item 2. The circuit board according to item 1.