JPH0793491B2 - Printed wiring board for surface mounting - Google Patents

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, and more particularly to a surface mounting printed wiring board having pads facing each other for mounting surface mounting components.

[0002]

2. Description of the Related Art In recent years, as printed wiring boards have become smaller, lighter and thinner, various electronic components that make up electronic circuits have been formed in the printed wiring boards. DI by inserting the component terminals (leads) into the DI
The P type has been changed to the SMD type (surface mount component) in which components are mounted without making holes in the printed wiring board, and the frequency of use of surface mount components is increasing. Such surface mounting of various electronic components is not limited to those having a large number of terminals such as ICs and transistors, but also capacitors,
It also covers parts such as resistors and diodes.

In order to attach the surface mount component to the printed wiring board, the printed wiring board is provided with pads corresponding to the terminals of each surface mount component, and the terminals of each surface mount component are soldered to these pads. Each is connected. Then, a conductive circuit electrically connected to the pad is connected,
A conductor circuit having a function as the entire printed wiring board is formed.

From the standpoint of the function of the conductor circuit,
Each wiring may have any shape, and normally, the wiring is performed so that the wiring length is as short as possible, as shown in FIG. 3, for the purpose of merely electrically connecting. .

[0005]

Generally, when attaching various electronic components to a printed wiring board, the terminals of the various electronic components are connected using solder.
When melted, it has the property of flowing over a heated metal surface along the metal surface. For example, the above-mentioned DIP
In the case of connecting the mold parts using solder, this DIP mold part has a physical supporting means of inserting its terminals into the holes provided in the printed wiring board. Does not matter in particular.

On the other hand, the surface mount component (3) mounted on the conventional surface mount printed wiring board (11) as shown in FIG. 3 is caused by the flow of molten solder or surface tension at the time of mounting. The force causes the terminals of the surface mount component (3) to move, resulting in a problem that the surface mount component (3) itself moves. In particular, in a two-terminal surface-mounted component, since the number of supporting points is small and unstable, a rotational force is easily applied, and the above-mentioned problems are prominent.

Specifically, as shown in FIG. 4, when the surface mount component (3) is mounted, the molten solder on the pads (2a) and (2b) is directed toward the conductor circuits (14a) and (14b) (in the figure). (→ mark), the terminals of the surface mount component (3) rotate and move in the direction of the mark in the figure along with this flow, resulting in the state of the surface mount component (3) as shown in FIG. Of.

Due to such movement of the surface mount component (3), the surface mount component (3) comes into contact with another component or another component pad, or the surface mount component (3) and the pad (2
There was a problem that a contact failure occurs due to the decrease of the contact area with a) and (2b).

An object of the present invention is to solve such conventional problems and to provide an excellent surface mounting printed wiring board which can improve surface mounting quality.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the means adopted by the present invention is "in a surface mounting printed wiring board having pads facing each other for mounting surface mounting components, The pads are connected to the portions located inside the facing sides of the pads facing each other, and are connected to the pads.
A printed wiring board for surface mounting, characterized in that it has a conductor circuit that bypasses the wiring.

That is, in the prior art, the shortest wiring, which is designed to minimize the wiring length for the purpose of only electrically connecting the conductor circuit to the pad, is connected to the pad in the present invention. The wiring is arranged on the inner side of the pads facing each other so as to bypass between the pads.

[0012]

As shown in FIGS. 1 and 2, according to the surface mounting printed wiring board (1) of the present invention, the pad (2a)
The conductor circuits (4a) and (4b) are located on the inner side of (2b) facing each other.
Connect the ends of each of these conductor circuits (4a) (4b)
Are formed so as to bypass the pads (2a) and (2b), the forces applied to the terminals of the surface mount component (3) in the opposite directions due to the flow of solder cancel each other out.
There is no force to move (3).

Particularly, in the present invention, the pads (2a) (2b)
By connecting the end of each conductor circuit (4a) (4b) to the part located inside the opposite side of, the force acting on each terminal of the surface mount component (3) at each pad (2a) (2b) is Since it works toward the pads (2b) and (2a) facing each other, the so-called Manhattan phenomenon in which the surface mount component (3) stands upright on one pad does not occur. In other words, if the end of each conductor circuit (4a) (4b) is connected to the portion located on the opposite outer side of the pads (2a) (2b), the molten solder will be the respective conductor circuits (4a) (4b). Will flow to the outside of each pad through
For (3), a force acts to pull this outward and to cause it. Therefore, if there is a large difference in solder connection strength between the two pads, a so-called Manhattan phenomenon occurs in which the surface mount component (3) stands upright on one of the pads.

On the other hand, in the printed wiring board according to the present invention, as described above, the end portions of the conductor circuits (4a) and (4b) are provided at the portions located inside the pads (2a) and (2b) facing each other. The molten solder flows inward by connecting
(3) is moved to the pad on the side where the solder connection is weak, and the force to bring it into close contact with the printed wiring board side works.
The Manhattan phenomenon does not occur because it has a function of compensating for the connection strength on the side of the pad with weak solder connection.

[0015]

The present invention will be described in detail with reference to the drawings. In the present invention, for example, the wiring conventionally arranged as shown in FIG. 4 is bypassed as shown in FIG. 1 or 2, and the direction of connection with the pads (2a) and (2b) is changed to the pad (2a). The solder flow directions are opposed to each other along the opposing line of (2b), and the wiring is bypassed between the pads. If the wiring is detoured within a range in which each dimension of the pad is tripled from the center of the pad, the mounting density of the surface mounting printed wiring board will not be significantly reduced. 1 and 2 each show an embodiment of the present invention, in which each of the conductor circuits (4a) and (4b) from the pair of pads (2a) and (2b) facing each other is the pad (4a ) (4b) on the opposite line, and the pad (4
It is connected by detour to the parts located on both inner sides of a) and (4b).

When mounting the surface mount component (3), a force is applied to the terminals of the surface mount component (3) in the direction of → in the figure due to the flow of solder. Since the directions are opposite, the force acting to move the surface mount component (3) is canceled and the surface mount component (3) does not move.

[0017]

As described above, according to the surface mounting printed wiring board of the present invention, the pads (2a) facing each other are provided.
Connected to the part located inside the opposite of (2b), these
Having conductor circuits (4a) (4b) bypassing each pad (2a) (2b)
Therefore, the force applied to the terminals of the surface-mounted component in the opposite direction due to the flow of the solder is reversed, and the force that acts to move the surface-mounted component is canceled, and the surface-mounted component does not move. Therefore, the movement of the surface mount component prevents the surface mount component from contacting other components or other component pads, and the contact failure due to the reduction of the contact area between the surface mount component and the pad does not occur. It is possible to provide an excellent printed wiring board for surface mounting.

In particular, in the printed wiring board according to the present invention, since the end portions of the conductor circuits (4a) and (4b) are connected to the portions located inside the pads (2a) and (2b) facing each other, melting is caused. Solder flows inward and moves the surface mount component (3) to the pad on the side with weak solder connection, and the force to adhere it to the printed wiring board side works, thus supplementing the connection strength on the side with weak solder connection. Since it acts, it does not cause the Manhattan phenomenon and does not cause contact failure between the surface mount component and the pad, and it is possible to provide a surface mount printed wiring board having excellent surface mount quality. .

[Brief description of drawings]

FIG. 1 is a partially enlarged plan view showing an embodiment of a surface mounting printed wiring board of the present invention.

FIG. 2 is a partially enlarged plan view showing an embodiment of the same surface mounting printed wiring board.

FIG. 3 is a partial plan view showing a conventional surface mounting printed wiring board.

FIG. 4 is a partially enlarged plan view showing a direction of a force applied to a surface mount component by molten solder in a conventional surface mount printed wiring board.

5 is a partially enlarged plan view showing a state where the surface mount components are connected in a moving state as a result of applying the force shown in FIG.

[Explanation of symbols]

 1 Surface Mounted Printed Wiring Board 2a, 2b Pad (land for soldering components) 3 Surface Mounted Component 4a, 4b Conductor Circuit

Claims (1)

[Claims] 1. A surface-mounting printed wiring board for mounting a surface-mounting component, the pad being opposed to each other, wherein each pad is connected to a part located inside the facing pad. Conductor circuit that bypasses
A printed wiring board for surface mounting, comprising: