JPS61208290A - Printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed wiring board suitable for incorporating a large number of integrated circuits and other electronic components whose lead wires are closely spaced.

[Conventional technology]

In general, a printed wiring board is coated with a soldering resistance layer called a solder resist so that only predetermined portions of the conductive pattern portion are soldered.

An example of this is shown in FIG. In the figure, the wiring 2 printed on one side of the insulating substrate 1 leaves a solder land of 3"ft, and a layer of solder resist 5 is formed on the other surface of the conductive pattern 4 by printing.

The lead terminal 8 of the electronic component 7 is inserted into the hole 6 from the back side of the board 1, bent on the printed side, and the excess is cut off to form a fixing part 9. In a printed wiring board incorporating electronic components in this manner, the printed surface is immersed in a molten solder tank or a jet solder tank to electrically and mechanically connect the lead wires and the wiring.

In the conventional circuit board, the distance between the solder land 3 and the conductive pattern 4 is large, and the distance between the conductive pattern 4 and the fixing part 9 of the lead terminal 8 is sufficient to prevent solder bridging from occurring.

[Problem that the invention seeks to solve]

However, in recent years, with the miniaturization of electrical equipment and advances in electronic component technology, more integrated circuits have been used and the density of component packaging has increased, and the spacing between adjacent circuit wires has gradually become smaller.

For example, if 10 or more wires are passed between soldering lands with leads clinched with a lead spacing of 10M11, the spacing between the wires will be 0.3 mx, and the insulation distance from the soldering lands will be approximately 0.4 mx. becomes smaller.

In high-density circuits, under the fixed part 9 of electronic components,
It becomes necessary to run wiring very close to this.

In such a case, in the conventional printed wiring board, the solder 10 of the fixing portion 9 in FIG. 3 and the wiring 4 are very close to each other, making it easy to cause solder bridging. This solder bridging is difficult for boys and difficult to correct.

[Means for solving problems]

In printing the soldering resistance layer of a printed wiring board, this invention is performed by applying a resistor from one direction perpendicular to the wiring, so that the wiring pattern slightly protruding from the surface of the insulating substrate can be printed. Focusing on the fact that the rising edge on the lower side of the printing direction is not completely covered by the solder resistance layer, we printed a second resistance layer on top of the first resistance layer by reversing the printing direction. This is what I did.

[Effect]

The second resistive layer printed in the reverse direction completely covers the exposed portion of the raised end surface of the wiring caused by uneven brushing during printing of the first resistive layer.

〔Example〕

The embodiment will be explained with reference to FIGS. 1 and 2. In the figure, 1 is an insulating substrate made of synthetic resin. Insulating substrate 1
A conductor 2 forms a conductive pattern 4 on one side of the substrate. A mounting hole 6 for a lead terminal 8 of an electronic component 7 is provided in the substrate 1, and a soldering land 3 is formed around the hole 6 using a conductor 2.

On the surface of the substrate 1 on which the conductive pattern 4 is formed, a first layer 5 of a solder resist 5 is formed over the entire surface except for the lands 3. After printing the first solder resist layer 5, the printing direction is reversed and the second solder resist layer 1 is printed.
2 is printed. This second layer 12 may be printed only between the two lands 3 or between the pattern 4 and the land 3 which are arranged close to the lands 3.

〔Effect of the invention〕

According to the present invention, even when the lead wire spacing of electronic components is small and a large number of wires are arranged at minute intervals within the lead spacing, solder bridging does not occur and electronic components can be mounted in high density. It is possible to provide a printed wiring board that can

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a printed wiring board of the present invention incorporating electronic components, Fig. 2 is a front view of the same printed wiring board showing a part of the metal, and Fig. 3 is a longitudinal sectional view of a conventional printed wiring board. be. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Conductor, 3... Soldering land, 4... Conductor pattern (wiring), 5... First layer of soldering resistance layer (solder resist), 6...Terminal hole, 7...Electronic component, 8...Lead terminal, 9...Fixing part, 10...Flower fastening

Claims (1)

[Claims] 1. A first layer of a soldering resistor layer is printed on the entire surface of the insulating substrate, leaving the soldering lands of the printed wiring formed on one side, in a direction perpendicular to the wiring, and on top of that, the printed wiring is reversed and printed on the lands. A printed wiring board characterized in that a second layer of a soldering resistance layer is printed on a portion of adjacent wiring.