JPH07106742A - Printed wiring board - Google Patents

Abstract

PURPOSE:To prevent the occurrence of such a trouble that a soldered section causes insufficient contact on one side or components come to stand up by symmetrically providing protruding sections which protrude by a specific length, have the same width as wiring has, and are made of the same material as that of a pair of pads for connecting components against the pads. CONSTITUTION:Protruded sections 5 which protrude by 0.05mm in minimum and 0.3mm in standard, have the same width as wiring 3 has, and are made of the same material as that of a pair of pads 2 of a printed wiring board for connecting components 4 are symmetrically provided against the pads 2 along the center lines of the pads 2 in the directions opposite to the direction of the wiring 3. Therefore, the occurrence of such a trouble that terminal sections cause insufficient contact on one side or the components 4 come to stand up can be prevented at the time of soldering the terminals of the components 4 to the pads 2, because the solder uniformly flows in all direction on the pads 2 and the components 4 are mounted at proper positions.

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.
When soldering the component terminals to the pair of component pads and mounting them, the component connects to the straight line connecting the pad centers,
The present invention relates to a printed wiring board which is mounted in a correct state substantially along the same without being greatly inclined.

[0002]

2. Description of the Related Art Conventionally, when connecting metal wiring to a pair of component pads formed of a metal which is easy to be familiar with solder, which is provided for soldering and mounting terminals of components on a printed wiring board, it is conventional. As shown in FIG. 3, the basic principle is to form wiring on an extension of a straight line connecting the centers of both component pads at least in the immediate vicinity of the component pads.
However, in recent years, it has become difficult to comply with the above-mentioned basic principle due to an increasing demand for mounting components on a printed wiring board at high density. For example, as shown in FIG. In some cases, there is no choice but to form wiring in a direction perpendicular to a straight line connecting the centers of a pair of component pads. However, in these drawings, 1 is a solder resist coating portion, 2 is a component pad, 3 is a component connecting metal wiring, and 4 is a component.

[0003]

However, the terminal of the component is actually mounted by soldering on the component pad in which the connection wiring is formed in the direction perpendicular to the straight line connecting the centers of the pair of component pads. Then, as shown in FIG.
It may be fixed at an angle with respect to the straight line connecting the centers of the pair of component pads, so that the soldered part may have poor contact on one side, or the component may stand up (it may be inclined to the board surface. There is a problem in that there is a problem such as a gap between the substrate surface and one side).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printed wiring board that does not cause the above-mentioned problems when mounting conventional components.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a pair of component connecting pads of a printed wiring board are provided in a direction opposite to the wiring direction with respect to the center line of each pad. Symmetrically, the minimum protrusion length is 0.0
It is decided to provide a protruding portion made of the same material as the pad having a width of 5 mm or more and a standard of 0.3 mm and a width equal to the width of the wiring.

[0006]

[Operation] When the cause of the above-mentioned malfunction in which the connection state of the parts is not normal is investigated, the solder melted on the part pad is pulled and flows in the direction of the metal wiring, and does not flow so much in the opposite direction. , It was found that there is a tendency that the flow does not flow symmetrically with respect to the pad center line orthogonal to the wiring connection direction. In the present invention, a kind of dummy metal wiring is formed so that such a flow of solder flows appropriately symmetrically in the direction opposite to the metal wiring.
In this way, when the pad protrusion is provided in the direction opposite to the metal wiring, the solder also flows in that direction due to the adhesive force of the solder on the pad metal surface and the cohesive force of the solder itself. Seem.

On the other hand, the wiring of the board surface around the whole of the parts connecting portion is completed so as to protect the board surface from oxidation and contamination by air and others, contact with other objects, etc., and to prevent solder from adhering. Later it will be covered with solder resist. In order to allow a sufficient margin for this solder resist coating operation, a gap called a resist escape of about 0.3 mm is formed around the component connection points including the component pads. Therefore, according to the present invention, the protruding portion of the metal pad provided on the side opposite to the connecting wiring of the component pad is exposed without being covered with this film even after the solder resist film is formed, and during the component connecting operation. According to the aim of the present invention, the molten solder is pulled in a direction opposite to the wiring, so that the solder flows substantially symmetrically with respect to the pad center line.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view for explaining a protrusion provided on a component pad according to the present invention. As is known, the original plate before processing of the printed wiring board is an insulating material, for example, on the entire surface of a glass fiber reinforced epoxy resin plate or a ceramic plate,
Copper foil is attached. From this copper foil, usually by photo-etching (photo (chemical) etching), unnecessary parts other than those that should become component pads and connection wiring are etched and removed by exposure method to complete component pads and wiring. Let After that, a solder resist is applied by, for example, a silk screen printing method, and then the component is fixed by soldering and mounted on a component mounting portion where the solder resist is not applied. After applying the solder resist, the substrate may be dipped in the molten solder to form the solder film only on the metal portion. As is well known, component connection is usually performed, for example, by reheating the solder film formed on the pad as described above to a molten (so-called reflow) state.
In FIG. 1, 1 is a solder resist coating portion, 2 is a component pad, and 5 is a protrusion portion according to the present invention.

FIG. 1 is a diagram for explaining the shape of a component pad with a protrusion according to the present invention. In practice, efforts are made to minimize the number of pattern masks for pads and wiring. Since the copper foil is first attached and unnecessary parts are removed as described above, the component pads are not isolated in this way, and the wiring is also included. Is formed. Further, the solder resist application portion 1 is shown by a broken line because it is applied on the component pad 2 and the wiring after they are formed. Further, although the projecting portion 5 is shown above and below both pads in FIG. 1, in actuality, one of the projecting portions 5 overlaps with the wiring and is not actually formed. The protrusion 5 is shown in FIG.
Although it is possible to prevent the component 4 from being obliquely mounted as shown in FIG. 5 if it is formed in the vertical direction of the pad as shown in FIG. Providing protrusions 5 also in the direction of extension of the straight line connecting the centers of the pads (that is, from the left pad to the left and from the right pad to the right in this figure) makes the solder flow more even on the pads. .

FIG. 2 is a view showing a state in which the present invention is carried out and the solder flows evenly on both pads and the parts are properly mounted. In the figure, 1 is a solder resist application portion, 2 is a component pad, 3 is a metal wiring, 4 is a component, and 5 is a protrusion according to the present invention. In this figure, the outline of the wiring 3 on the pad 2 is drawn, but this is for the purpose of explanation only.
No contour line actually occurs between the pad and the wiring formed by removing unnecessary portions from the copper foil.

[0011]

As described above, according to the present invention, when the terminals of the component are soldered to the pair of component pads, the solder flows almost uniformly in each direction on the pad, and the component is placed in the correct position. As a result of being mounted, it is possible to prevent an accident such as a contact failure of one side terminal portion or a part standing up as in the conventional case.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the shape of a component pad with a protrusion according to the present invention.

FIG. 2 is a view showing a state where solder is flown evenly on both pads and components are properly mounted by implementing the present invention.

FIG. 3 is a diagram showing a state in which wiring is formed on an extension of a straight line connecting the centers of a pair of component pads, which is a basic principle in the past when connecting wiring to the component pads.

FIG. 4 is a diagram showing a conventional example in which wiring is formed in a direction perpendicular to a straight line connecting centers of a pair of component pads in order to mount components at high density.

FIG. 5 is a view showing a conventional example in which a component is obliquely fixed to a straight line connecting the centers of component pads.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solder resist application part, 2 ... Component pad, 3 ... Metal wiring, 4 ... Component, 5 ... The protrusion part which concerns on this invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Miwako Kataoka, 3681 Hayano, Mobara, Chiba, Hitachi Device Engineering Co., Ltd. (72) Kazufumi Ikeda, 3681, Hayano, Mobara, Chiba, Hitachi Device Engineering, Ltd.

Claims (1)

[Claims] 1. A pair of component connecting pads of a printed wiring board, each of which has a minimum protrusion length of 0.05 mm or more and a standard length of 0.3 mm, symmetrically in a direction opposite to a wiring direction with respect to a center line of each pad. The printed wiring board is characterized in that a protruding portion made of the same material as the pad having a width equal to the width of the wiring is provided.