JPS6011655Y2 - printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed circuit board suitable for printed wiring in which electronic components are mounted at a high density, and particularly to a structure of a printed circuit board having soldered parts arranged close to each other.

Generally, printed wiring is done by immersing the soldered part of a conductive land for wiring into a molten solder bath or a jet solder bath, with many electronic components assembled on an insulating substrate, and then soldering the conductive land and the lead wires of the electronic components. It is attached.

In this type of soldering process, a layer of solder resist is formed in advance on areas where solder is not desired to adhere, but when the mounting density of electronic components is increased, the distance between the lead wires becomes closer, so solder resist such as solder bridges etc. This may cause defects.

For example, the solder resist 3 is applied to the wiring pattern of the conductive land 2 for wiring of the printed circuit board 1 shown in FIG. 1, leaving the soldered parts 4. Due to their presence, it occurs that these parts, which were originally designed to be insulated from each other, are connected by forming solder bridges.

The occurrence of such defects in solder bridges is largely influenced by the distance a between the soldered parts 4, but it has become necessary to make the distance a smaller than 0.5 mm in order to improve the mounting density of electronic components. Therefore, increasing this distance a from a design perspective will lead to a result that is contrary to the improvement of packaging density.

The present invention has been proposed in view of the above, and an object of the present invention is to provide a printed circuit board that reduces solder bridges that occur between soldered parts without reducing packaging density.

According to the present invention, a conductive land for wiring is formed independently on an insulating substrate in which through holes are arranged close to each other, and each soldered part is provided in correspondence with the position of each through hole. In a printed circuit board on which a solder resist is deposited, the soldered portions are formed in a substantially circular shape with arc-shaped notches on the sides that approach each other, and a solder bridge exists between adjacent soldered portions. Discloses a printed circuit board structure that prevents this from occurring.

What should be noted here is that because the soldered parts have crescent-shaped notches on the adjacent sides, the surface tension of the solder acts during the soldering process and causes them to stick to each other in the direction of separation, resulting in solder bridges. It is to prevent it.

In particular, when a crescent-shaped notch is formed by partially cutting out a terminal portion of a conductive land for wiring and forming a solder resist film, the surface tension of the solder acts to widen the separation distance a, preventing solder bridging. To obtain a good soldering structure by preventing the formation of solder cavities.

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

FIGS. 2 and 3 show a printed circuit board according to the present invention and its soldered state.

The printed circuit board 10 is composed of an insulating substrate 11, and a given number of through holes 12 for inserting lead wires are provided in the substrate 11 at positions close to each other.

A soldered portion 13 is provided corresponding to each through hole 12, and a wiring conductive land 14 extends from the soldered portion 13, and each conductive land 14 is formed independently and insulated from each other.

On the other hand, the solder resist 15 is formed around the entire circumference of the insulating substrate 11, leaving the soldered portion 13, and soldered so that it is soldered only to the half-soldered portion 13 immersed in a molten solder tank or a jet solder tank. A resist pattern is formed.

It should be noted here that the soldering portions 13 are formed into a substantially circular shape with arc-shaped notches on adjacent sides.

That is, arc notches are formed on the mutually adjacent sides of the circular terminal portions 16 of the conductive land 14 for wiring, and the entire area except the soldered portions 13 is covered with the solder resist 15 to form the arc-shaped notches 17. are doing.

As shown in FIG. 3, the printed circuit board 10 having the above-mentioned structure has the electronic components 18 assembled therein, and then the lead wires 19 are connected to the conductive lands 14 and the terminal portions 16 of the soldered portions 13 with solder 20 to form printed wiring. make up the body.

Here, the solder 20 is soldered in a direction in which the adjacent sides are separated from each other by the surface tension of the molten solder.

Therefore, formation of bridges between these adjacent solders 20 is prevented, and a printed wiring body with a good soldering structure is obtained in which no cavity is formed without solder.

When comparing a wiring body using the printed board of the present invention with a wiring body using a conventional printed board of the same size, we investigated the occurrence of defects in solder bridges and obtained the following results.

The printed board of the present invention has a bridging rate of 5 to 10%, and that of the conventional printed board is approximately 50%. The printed board 1 was different from the printed board 1 in terms of the presence or absence of a notch 17, but was tested with the same structure except for this.

4 and 5 show other specific examples, and the same parts as in FIG. 2 are indicated by the same symbols.

In this specific example, the notch 17 of the soldering portion 13 is substantially formed by the arcuate notch of the terminal portion 21 of the conductive land 14.

That is, in the soldering portion 13 to which the solder resist 15 is not deposited, the notch 17 is formed on the side of the terminal portion 21 that approaches the other terminal portion.

Therefore, even when this printed board is used, the adhering state of the solder 20 is tilted in the direction of separation from each other due to the surface tension of the molten solder similar to that shown in FIG. 3, as shown in FIG. 5, and the solder bridges It is effective in preventing this.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional printed board, Fig. 2 is a plan view of a printed board of the present invention, and Fig. 3 is a printed wiring body using the printed board of Fig. 2, line ■-m in Fig. 2. 4 is a plan view of another specific example shown in FIG. 2, and FIG. 5 is a sectional view of the printed board taken along the line ■-■ in FIG. 4, showing the state after soldering. It shows. 10...Printed board, 11...Insulating board, 12...Through hole for inserting lead wire, 1
3... Curved soldering part, 14... Conductive land, 1
5...Solder resist, 16.21...
Terminal part, 17... Notch.

Claims (1)

[Claim for Utility Model Registration] A conductive land for wiring having an independent terminal portion corresponding to each through hole is formed on an insulating substrate in which through holes are arranged close to each other, and this terminal portion is used as a soldering portion. In a printed circuit board for high-density mounting on which a solder resist is applied while leaving a portion, the terminal portion is cut out from a substantially circular land with an arc-shaped notch on the sides that approach each other, and a notch is formed on the side adjacent to the soldering portion. 1. A printed circuit board characterized in that the surface tension of molten solder is applied during soldering process to cause solder to adhere in directions that separate from each other, thereby preventing solder bridging between the soldered parts.