JP2561840B2 - Multilayer circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a multilayer circuit board from which information on an inner layer circuit can be easily read from the outside.

(Prior Art) With the recent trend toward miniaturization, high density, and high performance of electronic devices, the circuit boards used in electronic devices are being multi-layered.

Taking a four-layer board as an example, such a multilayer circuit board will be described with reference to FIG. 6, in which two second and third inner layer circuits 1 and 1 ′ and first and fourth outer layer circuits 2 are provided. 2 '
And an intermediate insulating layer 3, 3 ', 3 "between them. Usually, the second and third inner layer circuits 1, 1'are provided on both surfaces of the inner layer board, respectively. After the formation, a plurality of prepregs and a copper foil are sequentially laminated on both surfaces of the inner layer plate, and heat and pressure are applied to integrally laminate the layers, and then the outer layer copper foil is etched to form the first and fourth layers.
Are manufactured by forming the outer layer circuits 2 and 2 ', respectively. In a multilayer circuit board manufactured in this manner, after stacking outer layer prepregs, etc., the information about the inner layer circuit included is known, and in order to determine whether or not this is a planned circuit, it is a conventional multilayer circuit board. Using a counterbore drill on the circuit board, make a hole with a depth to reach each inner layer circuit and expose the shape of the exposed inner layer circuit or the symbols written in advance on the inner layer. It was done.

(Problems to be solved by the invention) However, in such a method, since the diameter of the hole drilled by the counterbore is as small as about 8 mm, the information obtained through this hole is quite small and the number of layers increases. At present, as the diversification of circuits and circuits continues to progress, this kind of information was not enough.

The present invention has been made in order to solve such a problem, and a multi-layer circuit in which a variety of information regarding an inner layer circuit can be easily known from the outside without making a hole by using a magnetic head or the like. It is intended to provide a substrate.

[Structure of the Invention] (Means for Solving the Problems) That is, in the multilayer circuit board of the present invention, in a multilayer circuit board having an internal layer circuit, information regarding this internal layer circuit is provided in a circuit unnecessary portion in the same layer as the internal layer circuit. It is characterized in that a pattern converted into a digital signal is formed by a magnetic material.

In the present invention, it is desirable to use a material having a strong coercive force such as ferrite or alnico as the magnetic body.

(Operation) In the multilayer circuit board of the present invention, the information about the inner layer circuit is described as a pattern converted into a digital signal by a magnetic material in the same layer as this circuit. When generated, the magnetic force lines can be easily detected from the outside of the multilayer circuit board by using a magnetic force line detector such as a magnetic head. Then, by analyzing the detected digital pattern, a great variety of information regarding the inner layer circuit can be immediately and clearly known.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 is a sectional view showing an embodiment of the multilayer circuit board of the present invention.

In the figure, reference numeral 4 has inner layer circuit boards on which inner layer circuits 5 and 5'having a predetermined pattern are formed on both front and back surfaces. Patterns 6 and 6 ′, which are digital signals of information regarding the inner layer circuits 5 and 5 ′, that is, information such as the circuit identification symbol and the date and time of manufacture, are formed of a magnetic material.

Further, a plurality of prepregs 7 and 7'are integrally laminated on both surfaces of the inner layer circuit board 4 on which the digital patterns 6 and 6'made of such a magnetic material are formed. , 7 ', the outer layer circuits 8, 8'are formed by etching copper foil, respectively.

In a multilayer circuit board having such a structure, a method for forming the digital patterns 6 and 6'made of a magnetic material on the same layer as the inner layer circuits 5 and 5'on the surface of the inner layer circuit board 4 is as follows. You can take various methods.

(1) As shown in FIG. 2, a pattern in which information on the inner layer circuit is converted into a digital signal on one surface of the thin plastic film 9 by an ink containing fine powder of magnetic substance by a printing method such as offset or silk screen. 10 is printed, and this film is attached to the circuit formation unnecessary portion on the inner layer circuit board 4.

(2) As shown in FIG. 3, the digital pattern 10 is directly printed on the circuit unnecessary portion on the surface of the inner layer circuit board 4 with the ink containing the fine magnetic powder.

(3) As shown in FIG. 4, a magnetic thin film or foil is applied to one side of a thin plastic film 9 and the digital pattern 10 of information is transferred by a method of hot stamping the film. Is pasted on the inner layer circuit board 4.

(4) A digital pattern made of a magnetic material is directly transferred onto the inner layer circuit board by a foil stamping method.

(5) As shown in FIG. 5, fine magnetic powder is applied thinly and evenly on a thin plastic film 9 and dried to form a fine magnetic powder layer 11, which is then formed on this layer. The magnetic head 12 is applied, and the magnetic head 12 is moved in close contact with the magnetic fine powder layer 11. In this way, the magnetic fine powder is rearranged on the film 9 so that the change in the magnetic force lines generated from the magnetic head 12 forms a digital pattern of information on the inner layer circuit, and then this film is attached to the inner layer circuit board 4. wear. Also, at this time, after the film on which the magnetic fine powder layer 11 is formed is attached to the inner layer circuit board 4, the magnetic head
A digital pattern may be formed on this layer 11 by applying 12.

(6) A magnetic fine powder layer is formed directly on the inner layer circuit board, and the magnetic fine powder of this layer is arranged using a magnetic head to form a digital pattern.

In this way, a digital pattern representing information about each inner layer circuit is formed using a magnetic material so as not to overlap in the vertical direction, and then a prepreg and a copper foil are sequentially laminated on this inner layer circuit board, By heat-press molding by the method, and finally by etching the outer layer copper foil, the multilayer circuit board of the embodiment is obtained.

In the multi-layer circuit board of the embodiment configured in this way, the detecting portion of the magnetic head is applied from above the outer layer circuits 8 and 8'and the lines of magnetic force are detected while gradually moving the magnetic head along the surface, Information about the inner layer circuit is read. That is, in the digital pattern formed by the magnetic material on the inner layer of the multilayer circuit board of the embodiment, the magnetic change detected by the magnetic head as the change of the magnetic force lines is converted into an electric signal and output to the magnetic head. Then, by converting the digitized electric signal into a normal display symbol, the information regarding the inner layer circuit can be easily read.

[Effects of the Invention] As apparent from the above description, in the multilayer circuit board according to the present invention, various information regarding the inner layer circuit can be easily obtained only by applying a magnetic head or the like to the outside and measuring and detecting the magnetic force lines emitted from the inner layer. I can know.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an embodiment of a multilayer circuit board of the present invention, and FIGS. 2 to 5 show a method for forming a digital pattern made of a magnetic material in each embodiment. FIG. 6 is a sectional view of a conventional multilayer circuit board. 1, 1 ', 5, 5' ... Inner layer circuit 2, 2 ', 8, 8' ... Outer layer circuit 4 ... Inner layer circuit board 6, 6 ', 10 ... Digital pattern 7,7' made of magnetic material ...... Thin plastic film 11 …… Magnetic powder layer 12 …… Magnetic head

Claims (2)

(57) [Claims] 1. A multi-layer circuit board having an inner layer circuit,
A multilayer circuit board, characterized in that a pattern obtained by converting information on the inner layer circuit into a digital signal is formed in a circuit unnecessary portion on the same layer as the inner layer circuit by a magnetic material. 2. A digital pattern made of the magnetic material,
The multilayer circuit board according to claim 1, which is formed by arranging fine magnetic powders using a magnetic head.