JPH07111381A - Printed circuit board - Google Patents

Abstract

PURPOSE:To provide a means for positively performing soldering while securing the amount of solder without increasing the thickness of a solder plating part. CONSTITUTION:A solder plating part 5 is formed also on a lead 4 and a deburring part 8 which continue a land 2 and are narrower than the land 2 is formed in addition to the land 2. Therefore, when the solder plating part 5 is heated and melted, the molten solder is absorbed onto the wide land 2 from the narrow area on the lead 4 and that on the deburring part 8, thus firmly soldering the electrode on electronic component 6 and easily controlling the amount of solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board for soldering an electronic component to a land of a circuit pattern.

[0002]

2. Description of the Related Art As a method of soldering an electronic component to a printed circuit board, a solder plated portion is previously formed on a land of a circuit pattern on the upper surface of the printed circuit board by a plating means, and an electrode of the electronic component is landed on the solder plated portion. Then, a method is known in which the solder plated portion is heated in a heating furnace to melt and solidify. Such a soldering method using the solder-plated portion has an advantage that solder can be easily formed even on a minute land, as compared with other methods in which the solder paste is applied to the land by screen printing.

[0003]

In order to firmly solder the electronic component to the land, the amount of solder in the solder-plated portion must be increased. To increase the amount of solder, the thickness of the solder-plated portion must be increased. Must be thickened. However,
The thicker the solder-plated part, the longer it takes to form the plating, and the higher the cost. Therefore, the solder-plating method is not commonly used at present, and the screen using the cream solder described above is used. The printing method is often used.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a printed circuit board having a solder-plated portion that can easily secure the amount of solder.

[0005]

For this reason, in the printed circuit board of the present invention, not only the land but also the solder plating portion is formed not only on the upper surface of the circuit pattern narrower than the land continuous with the land. Is.

[0006]

According to the above construction, when the electronic component is mounted on the printed board and the solder plating portion is heated and melted in the heating furnace, the molten solder is spread from the narrow portion to the wide portion due to the surface tension. It is drawn to the land. Therefore, the amount of solder on the land increases, and the electrode of the electronic component can be firmly soldered to the land.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the drawings.

FIG. 1 is a plan view of a printed circuit board. Lands 2 and 3 are formed on the upper surface of the printed circuit board 1. The lands 2 and 3 are formed at the tips of the leads 4, and the lands 2 and 3 and the leads 4 form a circuit pattern.

FIG. 2 is a partially enlarged plan view of the land 2, and FIG. 3 is a sectional view. Electrodes 7 of a rectangular electronic component 6 such as a capacitor chip and a resistance chip are mounted on the land 2. The solder-plated portion 5 is formed on the upper surface of the land 2 and on the upper surface of the lead 4 which is continuous with the land 2 and is narrower than the land 2. As described above, the solder plating portion 5 is formed not only on the land 2 but also on a part of the lead 4 continuous to the land 2, so that the formation area of the solder plating portion 5 is widened and the amount of solder is increased. Although not shown, the resist film is coated on a portion other than the upper surface of the land 2.

As shown in FIG. 3, the electronic component 6 is mounted on the printed circuit board 1, and the printed circuit board 1 is sent to a heating furnace to be heated. Then, the solder plating portion 5 is heated and melted.
The surface tension in the molten state is larger on the narrow lead 4 than on the wider land 2. Therefore, the molten solder on the lead 4 is attracted to the land 2 as shown by the arrow in FIGS.
The electrode 7 is firmly soldered to the land 2 as shown in FIG. In the figure, 5a indicates melted and solidified solder.

As described above, according to this method, when the solder-plated portion 5 formed on the lead 4 is heated and melted,
Because it is attracted to the land 2 due to the difference in surface tension,
The electrode 7 can be firmly soldered to the land 2 by increasing the amount of solder on the land 2 without increasing the thickness of the solder plating portion 5.

Further, according to this method, it is possible to easily manage the amount of solder. That is, in FIG. 2, the longer the length L of the solder-plated portion 5 formed on the lead 4 is, the more the amount of solder is attracted to the land 2 and the larger the amount of solder. Therefore, by changing the length L according to the type of the electronic component 6,
An optimum amount of solder can be set for the electronic component 6.

FIG. 5 is a partially enlarged plan view of a printed circuit board 1 according to another embodiment of the present invention. In this structure, a flash-out portion 8 is continuously formed at the tip of the land 2, and the solder-plated portion 5 is also formed in the flash-out portion 8. The exposed portion 8 is narrower than the land 2. The exposed portion 8 is provided so as to project from the tip of the land 2 located immediately below the electronic component 6 so as not to interfere with the wiring of the circuit pattern.

Therefore, also in this product, when the electronic component 6 is mounted and the solder-plated portion 5 is heated and melted, the melted and solidified solder 5a is attracted to the wide land 2 as shown by the arrow, and the electrode of the electronic component 6 is Can be firmly soldered to the land 2. Of course, the amount of solder can be controlled by changing the area of the flash-out portion 8. In this embodiment, the solder plated portion 5 is also formed on the lead 4.
It is not always necessary to form the solder plating portion 5 on the upper portion.

FIG. 6 shows still another embodiment. The pin type electrode of the electronic component 6 is mounted on the land 3. In this case as well, the solder amount is secured by forming the solder plating portion 5 on a part of the lead 4 and the protruding portion 9. Also in this case, the projecting portion 9 is provided so as to project from the tip of the land 3 located immediately below the electronic component 6.

[0016]

As described above, in the electronic component of the present invention, the solder plating portion is formed on the upper surface of the land and the circuit pattern which is continuous with the land and is narrower than the land. By being attracted to the land, the amount of solder on the land can be secured by the solder-plated portion having the same thickness as the conventional one, and the electrode of the electronic component can be firmly soldered to the land. Further, since the amount of solder can be adjusted by changing the formation area of the solder plated portion, it is possible to easily secure the optimum amount of solder according to the type of electronic component.

[Brief description of drawings]

FIG. 1 is a plan view of a printed circuit board according to an embodiment of the present invention.

FIG. 2 is an enlarged plan view of a land portion of a printed circuit board according to an embodiment of the present invention.

FIG. 3 is a sectional view of a land portion of a printed circuit board according to an embodiment of the present invention.

FIG. 4 is a sectional view of a printed circuit board according to an embodiment of the present invention.

FIG. 5 is a partially enlarged plan view of a printed circuit board according to another embodiment of the present invention.

FIG. 6 is a partially enlarged plan view of a printed circuit board according to an embodiment of the present invention.

[Explanation of symbols]

 1 Printed circuit board 2,3 Land 4 Lead 5 Solder plating part 8,9 Overhang part

Claims (1)

[Claims] 1. A printed circuit board having a circuit pattern having lands formed on an upper surface thereof, wherein a solder-plated portion is formed on an upper surface of a circuit pattern which is continuous with the land and is narrower than the land. Characterized printed circuit board.