JPH10270812A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improved the insulating characteristic between two wiring conductors arranged on a substrate at a constant interval by applying a solder resist to the two wiring conductors and performing silk printing on the solder resist on at least one wiring conductor. SOLUTION: A laminated board clad with copper foil on its surface is placed on a substrate 1 made of glass-epoxy, etc., and pattern ink is printed on the remaining part of the substrate as a wiring pattern (wiring conductors). The unnecessary part of the copper foil except the pattern ink is etched off and, in addition, the pattern ink printed on the wiring conductors 5 is removed. After a solder resist 6 is printed on the wring conductors 5, an insulating silk 7 film (having a thickness of about 7-20 μm and indicting parts numbers, etc.) is printed on the solder resist 6. The dielectric strength between the conductors 5 and 5 is improved by additionally printing the silk film 7 on the solder resist 6 arranged on and between the conductors 5 and 5.

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 designed to satisfy a dielectric strength specified by, for example, safety standards.

[0002]

Generally, when manufacturing and selling electrical products, it is necessary to design the electrical products so as to satisfy safety standards such as the Electrical Appliance and Material Control Law and UL and CSA provided in each country. There is. For example, a printed wiring board (hereinafter, referred to as a wiring board) is disposed adjacently on the wiring board so as to ensure a minimum withstand voltage.
A minimum pattern gap (predetermined interval) to be secured for one wiring pattern is determined.

As an example, in the UL / CSA standard, the minimum pattern gap is defined for each product. For example, for a programmable controller used in a 200 V system, a resist (solder resist) is applied on a wiring pattern. Is defined to secure a pattern gap of 0.75 mm or more when the resist is applied, and 1.9 mm or more when the resist is not applied.

[0004] In addition, in these safety standards, apart from the minimum pattern gap, the withstand voltage to be ensured for each product (apparatus) for various uses is specified.
In the CSA standard, about 1500 VAC (=
1000V + Rated voltage (240V) × 2 = 1480V)
It is determined to ensure the above-mentioned dielectric strength. Such a withstand voltage is, specifically, a circuit board provided corresponding to a part directly touched by a user, such as an operation part provided with an operation switch, and another circuit part or a housing. It is determined for the ground.

[0005] Therefore, even if the wiring patterns are arranged so as to secure the minimum pattern gap, it may not be possible to secure the withstand voltage for each product. In such a case, it is necessary to arrange the wiring patterns so as to have a gap larger than the minimum pattern gap, and there is a problem that the area of the wiring board must be increased.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an insulation according to safety standards required for various products without requiring a larger area required for disposing wiring conductors. An object of the present invention is to provide a printed wiring board capable of satisfying a withstand voltage.

[0007]

According to the printed wiring board of the present invention, silk printing is performed on at least one of the solder resists disposed on the two wiring conductors disposed at a predetermined interval. Since the insulation characteristics between the two wiring conductors are improved, it is possible to obtain a higher breakdown voltage than that secured at a predetermined interval between the two.

Therefore, for example, even if the predetermined interval merely satisfies the minimum pattern gap defined by the safety standard, the insulation withstand voltage required by the safety standard from a different viewpoint cannot be obtained. Is applied, the required withstand voltage can be ensured without further expanding the pattern gap, and the whole can be made compact without requiring a larger area of the substrate. .

According to the printed wiring board of the present invention, silk printing is performed also on the solder resist disposed between the two wiring conductors, so that a higher dielectric strength can be ensured.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a printed wiring board (hereinafter, referred to as a wiring board) used for an operation section of a programmable controller will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view of a wiring board schematically illustrating a manufacturing process of the wiring board according to a characteristic part of the present invention.
It is the same as the conventional manufacturing process.

First, a laminate 3 having a copper foil 2 having a thickness of about 18 μm is prepared on a substrate 1 made of, for example, glass epoxy having a thickness of about 1.6 mm (see FIG. 2A). Next, a pattern ink (etching resist) 4 is printed on a portion where the copper foil 2 is left as a wiring pattern (wiring conductor) (see FIG. 2B).

Here, the interval between the pattern inks 4 and 4, that is, the interval between the wiring patterns formed thereunder is, for example, the minimum pattern gap 0 .0 applied to the 200V type programmable controller in the UL / CSA standard. It is set so as to satisfy 75 mm (predetermined interval) or more (when there is a solder resist).

Next, an unnecessary portion of the copper foil 2 (that is, a portion other than the portions where the pattern inks 4 and 4 are printed) is removed by etching (see FIG. 2C). Then, a wiring pattern (wiring conductor) is provided below the pattern inks 4 and 4.
5, 5 are formed. Then, the wiring patterns 5, 5
The upper pattern inks 4 and 4 are removed (FIG. 2D).
reference).

Next, a solder resist 6 is printed on the wiring patterns 5 and 5 which do not need to be soldered (see FIG. 2E). The thickness of the solder resist 6 is, for example, about 7 to 20 μm.

Then, the silk 7 is placed on the solder resist 6.
Print. Usually, the silk 7 is printed to indicate the position of the component on the substrate, the component number, and the like.
Here, at the same time as performing them, the wiring patterns 5, 5
The silk 7 is also printed on the upper part of and above the space between the two (see FIG. 2 (f)). The thickness of the silk 7 is substantially the same as the thickness of the solder resist 6. Through the above manufacturing steps, a wiring board is created. FIG. 1 shows a plan view of a portion corresponding to the wiring patterns 5 and 5 of the prepared wiring board.

As described above, in the UL / CSA standard,
Since a programmable controller used in a 200 V system is specified to ensure a withstand voltage of 1500 VAC or more, in a conventional wiring board, in order to ensure the withstand voltage, the wiring interval between the wiring patterns 5 and 5 is required. It was necessary to widen the minimum pattern gap of the UL / CSA standard.

In order to cope with this, in the present embodiment, silk 7 having an insulating property is further printed on the wiring patterns 5 and 5 and on the solder resist 6 disposed therebetween. Thereby, the dielectric strength between them can be improved. Alternatively, a larger margin can be secured for a certain dielectric strength voltage. Therefore, since it is not necessary to increase the pattern gap of the wiring patterns 5 and 5, it is possible to reduce the size of the wiring board without requiring a larger area.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or extensions are possible. The silk 7 does not need to be printed on the solder resist 6 disposed on the wiring patterns 5 and 5 and at a portion between the two, and the solder resist disposed on at least one of the wiring patterns 5 and 5 is not required. 6 may be printed. Even in such a case, it is possible to improve the withstand voltage. Also, as shown in FIG.
When the wiring pattern (wiring conductor) 8 and the through-hole (wiring conductor) 9 for exposing the conductor portion are arranged close to each other on the substrate 1, the distance between them is set to the minimum pattern defined by the UL / CSA standard. After forming the gap, the silk 7 may be printed above a portion where the wiring pattern 8 is opposed to the through hole 9.

The present invention is not limited to the programmable controller, but can be applied to any electric product, and it is only necessary to comply with safety standards corresponding to different products. Further, the minimum pattern gap and the dielectric strength of the wiring patterns 5 and 5 are not limited to those conforming to the UL / CSA standard, but may be appropriately adapted according to the standards of each country such as the Electrical Appliance and Material Control Law and VDE and BSI. The thicknesses of the substrate 1, the wiring patterns 5, 5, the solder resist 6 and the silk 7 are merely examples, and may be changed as appropriate.

[Brief description of the drawings]

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

FIG. 2 schematically shows a manufacturing process of a printed wiring board;
Schematic sectional view of the main part of a printed wiring board

FIG. 3 is a diagram corresponding to FIG. 1 when a through hole and a wiring pattern are arranged close to each other;

[Explanation of symbols]

5, 5, and 8 are wiring patterns (wiring conductors), 6 is a solder resist, 7 is silk, and 9 is a through hole (wiring conductor).
Is shown.

Claims (2)

[Claims] 1. A printed circuit board on which a solder resist is disposed on a wiring conductor, wherein a solder resist is disposed on two wiring conductors which are disposed at a predetermined interval to secure a dielectric strength among the wiring conductors. A printed wiring board, characterized in that at least one of the printed wiring boards is subjected to silk printing to further improve the dielectric strength. 2. The printed wiring board according to claim 1, wherein the silk printing is also performed on a solder resist disposed between the two wiring conductors.