JPH04217388A - Printed wiring board - Google Patents

Abstract

PURPOSE:To move a sheet lead wire virtually the center of a land in its width direction by installing a narrow land section which has virtually the same thickness with that of the sheet lead wire and forms the center of the land width direction, and using the self-alignment force based on the surface tension of plating. CONSTITUTION:When a circuit component is installed on a printed wiring board, its installation position is deviated so that a sheet-like lead wire 4a may be installed and one-sided to the right direction. Then, a first solder 5a and a second solder 5b are melted where the first solder 5a comprises a soldering layer formed on the surface of a narrow section 3a of a land 3 and the second solder 5b comprises a soldering layer formed on a wide land section 3b. The sheet-like lead wire 4a is moved in the direction marked with an arrow 7 by the self-alignment force based on surface tension in the first solder 5a and the second solder 5b. The sheet-like lead wire 4a is attracted up to the position where the right end of the sheet-like lead wire 4a is aligned with the right end of the wide section of the land 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in printed wiring boards on which surface-mounted circuit components are mounted.

0002

2. Description of the Related Art FIG. 6 is a plan view showing a conventional printed wiring board. In the figure, 1 indicates an insulating substrate 2 and this insulating substrate 2.
This is a printed wiring board equipped with a rectangular land 3 made of a conductor layer formed by a photoetching method or the like on the surface of the printed wiring board 1. Plate lead 4 of circuit component 4 consisting of components
It is formed wider than the width of a.

Next, mounting of circuit components 4 on printed wiring board 1 will be explained. First, by dip soldering method etc.
A solder layer is formed on the surface of the land 3. The circuit component is arranged on the printed wiring board 1 so that the plate-shaped lead 4a of the circuit component 4 is in contact with the surface of the land 3 on which the solder layer is formed, and the solder layer is melted by a reflow soldering method or the like to form a plate-shaped lead 4a of the circuit component 4. By soldering leads 4a to lands 3, circuit components 4 are mounted on printed wiring board 1.

0004

[Problems to be Solved by the Invention] Since the conventional printed wiring board is constructed as described above, as shown in FIG. Figure 8 (A)
As shown in the figure, the solder 5 melts during soldering, and the solder 5 melts during soldering.
The plate-shaped lead 4a moves in the direction of arrow 7 due to the self-alignment force due to surface tension in the directions of arrows 6a and 6b, and the plate-shaped lead 4a is moved to a position where the right end of the plate lead 4a and the right end of the land 3 are aligned. It is drawn to the land 3, and the plate-shaped lead 4a is soldered to the land 3 at that position.

In this way, for land 3, as shown in FIG.
As shown in , since the plate-shaped lead 4a is soldered at a position offset to the right, a fillet 5c is formed at the left end of the plate-shaped lead 4a, but no fillet is formed at the right side. The bonding area of the solder is small, the soldering strength is weak, and the reliability is low such that the soldering may come off due to expansion and contraction of the solder, and it is difficult to visually inspect whether there is leakage with the adjacent land 3 when mounting circuit components. , and if excess solder adheres during the formation of the solder layer to the lands 3, this excess solder flows out between the lands during mounting, causing problems such as leakage.

The present invention has been made to solve the above-mentioned problems, and even if the plate-like leads of the circuit components to be mounted are disposed on the land with an offset to the left or right, the surface tension of the solder The self-alignment force based on the base moves the plate-shaped lead to the approximate center of the land in the width direction, and the plate-shaped lead is soldered to the approximate center of the land, increasing mounting accuracy and increasing soldering strength and reliability. It is easy to visually inspect for leakage from adjacent lands when mounting circuit components, and even if excess solder adheres to the land when forming the solder layer on the land, this excess solder can be easily inspected. The purpose is to obtain a printed wiring board that does not cause leakage between lands.

[0007]

[Means for Solving the Problems] The printed wiring board according to the present invention has a land wider in width than the plate-like lead of a circuit component to be mounted, which has approximately the same width as the plate-like lead, and has a width direction of the land. A narrow land portion is provided centered on the center.

[0008]

[Function] When mounting circuit components, the printed wiring board of the present invention is capable of self-sufficiency based on the surface tension of the solder in the narrow land portion, even if the plate leads of the circuit component are arranged offset to the right or left of the land. The alignment force moves the plate-shaped lead to approximately the center of the land and solders the land. Further, excess solder on the land portion is absorbed by the narrow land portion.

[0009]

[Example] Example 1. FIG. 1 is a plan view showing a printed wiring board according to an embodiment of the present invention. FIG. 2 is a plan view showing the detailed structure of section A in FIG. In these figures, the difference from FIG. 6 is that the land 3 is made of a conductive layer that extends in the longitudinal direction of the plate-shaped lead 4a of the circuit component 4 to be mounted and is wider than the width of the plate-shaped lead 4a. A narrow land portion 3a having approximately the same width as the plate-like lead (4a) and centered at the center 7 of the land 3 in the width direction is provided in the middle of the land 3. and a wide land portion (3b).

Next, the mounting of circuit components 4 on printed wiring board 1 will be explained. First, by dip soldering method etc.
A solder layer is formed on the surface of the land 3. The circuit component 4 is placed on the printed wiring board 1 so that the plate-shaped lead 4a of the circuit component 4 is in contact with the surface of the land 3 on which the solder layer is formed, and the solder layer is melted by a reflow soldering method or the like. Printed wiring board 1 is assembled by soldering plate-shaped leads 4a to lands 3.
Circuit components 4 are mounted on top.

When the circuit components 4 are placed on the printed wiring board 1, if the placement position is shifted and the plate-shaped leads 4a are placed off to the right as shown in FIG. 3(A), reflow A first solder 5 consisting of a solder layer formed on the surface of the narrow land portion 3a of the land 3 during soldering using a soldering method or the like.
The second solder 5b made of the solder layer formed on the surfaces of the wide land portions 3a and 3b is melted, and the arrows 9a, 9b, 10a, 10b in the first and second solders 5a, 5b are melted.
The plate-shaped lead 4a moves in the direction of arrow 7 due to the self-alignment force based on the surface tension in the direction shown in FIG.
As shown in B), the plate lead 4a is pulled to a position where the right end of the plate lead 4a and the right end of the wide land portion 3b of the land 3 are aligned.

Thereafter, the plate-shaped lead 4a further moves in the direction of arrow 7 due to the self-alignment force based on the surface tension of the first solder 5a in the directions of arrows 9a and 9b, as shown in FIG. 3(C). It is drawn to the center of the land 3, held at this position, and soldered to the land 3, and fits 5c are formed at both left and right ends of the plate-shaped lead (4a).

Example 2. FIG. 4 is a plan view of a printed wiring board according to another embodiment of the present invention, which differs from that shown in FIG. The function is the same as that described above in that the narrow land portion 3a is formed with the narrow land portion 3a centered at the center 8 in the width direction of the portion 3, and therefore a description thereof will be omitted.

Example 3. FIG. 5 is a plan view of a printed wiring board according to another embodiment of the present invention, and the difference from that shown in FIG.
The function is the same as described above, in that both ends of the longitudinally intermediate portion are notched in an arc shape to form a narrow land portion 3a centered on the widthwise center 8 of the land 3, so a description thereof will be omitted. do.

Note that in the above embodiment, both ends of the land 3 in the longitudinal direction are notched, but the present invention is not limited to this; for example, both ends of one end of the land 3 may be cut out in the same manner as described above. good.

[0016]

[Effects of the Invention] As described above, according to the present invention, the circuit components to be mounted are arranged offset on the printed wiring board, and the plate-shaped leads of the circuit components are arranged offset to the left and right on the lands. However, during soldering by reflow etc., the plate-shaped lead is drawn to the approximate center of the land and soldered due to the surface tension of the solder on the narrow land, correcting the mounting deviation and improving the mounting accuracy. , it is easy to visually inspect for leakage from adjacent lands, and fillets are formed at both ends of the plate-shaped lead, so the solder bonding area is large, the soldering strength is strong, and the solder does not expand or contract. This prevents the solder from coming off and improves reliability. Furthermore, even if excess solder adheres when forming a solder layer on the land, the excess solder is absorbed into the narrow land portion during soldering, thereby preventing leakage from adjacent lands.

[Brief explanation of the drawing]

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

FIG. 2 is a plan view showing the detailed structure of section A in FIG. 1;

FIG. 3 is a cross-sectional view showing the situation when the plate-shaped lead is soldered to the land shown in FIG. 1;

FIG. 4 is a plan view showing a printed wiring board according to another embodiment of the invention.

FIG. 5 is a plan view showing a printed wiring board according to another embodiment of the invention.

FIG. 6 is a plan view showing a conventional printed wiring board.

7 is a plan view showing how plate-shaped leads are arranged on the lands shown in FIG. 6; FIG.

8 is a cross-sectional view showing a situation when the plate-shaped lead is soldered to the land shown in FIG. 6; FIG.

[Explanation of symbols]

1 is a printed wiring board, 3 is a land, 3a is a narrow land portion, 3
b is a wide land portion, and 4a is a plate-shaped lead.

Claims (1)

[Claims] 1. A land extending in the longitudinal direction of a plate-shaped lead of a circuit component to be mounted and having a width wider than the width of the plate-shaped lead to which the plate-shaped lead is soldered, The land has approximately the same width as the above-mentioned plate-shaped lead,
A printed wiring board characterized in that a narrow land portion is provided centered at the center in the land width direction.