JPH03255698A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a printed wiring board where screen printings can be sharply lessened in number of times and electromagnetic noises can be prevented from radiating to be manufactured at a low cost by a method wherein a ferrite layer is formed on the specific part of an insulating board on which a circuit of conductor has been formed so as to cover the circuit concerned. CONSTITUTION:A ferrite layer 3 is formed on an insulating board 1 on which a circuit 2 has been formed excluding a through-hole and a competent mounting pads. The ferrite layer 3 is formed through such a method that solid ferrite is ground into powder and mixed with thermosetting resin whose main component is epoxy resin into ink, and then the ink is printed to form the layer 3. The component of ferrite to use and the thickness of the ferrite layer 3 are determined according to the frequency of electromagnetic noises to be absorbed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed wiring board and a manufacturing method thereof, and more particularly to a printed wiring board capable of absorbing electromagnetic waves and a manufacturing method thereof.

[Conventional technology]

In recent years, regulations regarding electromagnetic waves (noise) emitted from electronic devices have been tightened.

In order to suppress this electromagnetic wave emission, Fig. 3(a) to (d)
), there is a printed wiring board in which a conductive layer 6 is formed of a conductive resin such as a copper base on a circuit 2 on the surface of the printed wiring board.

[Problem to be solved by the invention]

The conventional printed wiring board described above is shown in FIGS. 3(a) to (d).
), since the conductive layer 6 is formed on the circuit 2, the insulating layer 5 is required to insulate the circuit 2 and the conductive layer 6.

This insulating layer 5 is formed by screen printing an insulating resin, but has the disadvantage that screen printing is required two to three times to prevent pinholes.

Further, the conductive layer 6 and the protective layer 7 formed thereon are also formed by screen printing. Therefore, a total of 4 to 5 screen printing steps are required, which is a disadvantage of causing an increase in the cost of printed wiring boards according to the prior art.

An object of the present invention is to provide a printed wiring board that requires less screen printing and is inexpensive, and a method for manufacturing the same.

[Means to solve the problem]

The printed wiring board of the present invention has a ferrite layer at a predetermined portion on an insulating substrate having a circuit formed of conductors.

The method for manufacturing a printed wiring board of the present invention includes the step of forming a ferrite layer on a predetermined portion of an insulating substrate on which a circuit is formed using a conductor so as to cover the circuit.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) and 1(b) are sectional views showing the order of steps for explaining the manufacturing method of the first embodiment of the present invention.

In the first embodiment, as shown in FIG. 1(a), a ferrite layer 3 is formed on an insulating substrate 1 on which a circuit 2 is formed, and component mounting parts such as through holes and pads are formed as shown in FIG. 1(b). Escape and form.

The ferrite layer 3 can be formed by, for example, pulverizing solid ferrite, mixing it with a heat-effect resin mainly composed of epoxy resin, making an ink, and screen-printing the ink. The components of the ferrite used and the thickness of the ferrite layer 3 may be determined depending on the frequency of the noise that is not absorbed.

FIGS. 2(a) to 2(c) are cross-sectional views showing the manufacturing method of the second embodiment of the present invention in the order of steps.

In the second embodiment, as shown in FIG. 2(a), a solder mask 4 is applied to an insulating substrate 1 on which a circuit 2 is formed, as shown in FIG. The ferrite layer 3 is formed by exposing, developing and curing, and as shown in FIG. 2(C), the ferrite layer 3 is formed on the solder mask 4 by, for example, screen printing the ferrite ink described in the first embodiment. do.

By forming the solder mask 4 under the ferrite layer 3, solder bridging during component mounting can be reduced.

〔Effect of the invention〕

As explained above, in the present invention, there is no need to screen print the conductive layer, insulating layer, and protective layer, and it is sufficient to simply print the ferrite layer, so the number of screen prints can be significantly reduced, and the radiation of electromagnetic noise can be reduced. This has the effect of making it possible to manufacture printed wiring boards at low cost.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are cross-sectional views showing the manufacturing method of the first embodiment of the present invention in the order of steps, and FIGS. 2(a)-(
C) is a cross-sectional view shown in the order of steps to explain the manufacturing method of the second embodiment of the present invention, and FIGS. 3(a) to (d) are cross-sectional views shown in the order of steps to explain an example of the conventional manufacturing method. It is. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Circuit, 3... Ferrite layer, 4... Solder mask, 5... Insulating layer, 6...
- Conductive layer, 7... protective layer. (0) (bn first haze

Claims (2)

[Claims] (1) A printed wiring board characterized by having a ferrite layer at a predetermined portion on an insulating substrate on which a circuit is formed using a conductor. (2) A method for manufacturing a printed wiring board, comprising the step of forming a ferrite layer on a predetermined portion of an insulating substrate on which a circuit is formed using a conductor so as to cover the circuit.