JP2002271039A - Multilayer board and its machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed board in which an insulating layer only can be eliminated when machining is performed by using a laser beam. SOLUTION: The multilayer board is provided with a first and second metal layers 2, 3 which are electrically connected with electronic components to be mounted, and an insulating layer 1 which is formed between the first and second metal layers 2 and 3 and isolates them from each other. A reflecting layer for reflecting the laser beam which is cast in order to form a hole in the insulating layer 1 is formed between the insulating layer 1 and the first metal layer 2 or the second metal layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer substrate and a method for processing the same, and more particularly, to a multilayer substrate processed by a laser beam and a method for processing the same.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
The multilayer printed circuit board having each copper foil 102 covering each insulating layer 101 made of resin or the like formed so as to sandwich the inner copper foil 103 by drilling a hole in one copper foil 102 using a drill or the like And an external electronic component can be electrically connected by a conductor such as solder.

A multilayer printed circuit board having an insulating layer 109 made of a photosensitive resin or the like formed on the surface of each copper foil 102 formed with an insulating layer 101 interposed therebetween as shown in FIG. A hole is provided in 109 so that the copper foil 102 and an external electronic component can be electrically connected by a conductor such as solder.

Further, as shown in FIGS. 9 and 10, in order to reduce the diameter of holes to be drilled in the copper foil 102 and the like and to increase the precision, as shown in FIGS. In some cases, holes are formed using a laser beam 108 such as a carbon dioxide gas laser.

[0005]

However, when a hole is formed in a multilayer printed circuit board using a carbon dioxide laser or the like, if the power of the laser light emitted from the carbon dioxide laser is large, the copper foil of the inner layer is formed together with the insulating layer. When the power of the laser beam is small, the insulating layer may not be sufficiently removed. Therefore, in the plating process for forming the conductive layer, there may be a case where plating is unnecessary and reliability of electrical connection is reduced.

Accordingly, an object of the present invention is to provide a multilayer printed circuit board capable of removing only an insulating layer when processing with a laser beam.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides first and second metal layers electrically connected to electronic components to be mounted, and between the first and second metal layers. Irradiation for providing a hole in the insulating layer between the insulating layer and the first or second metal layer in a multilayer substrate having an insulating layer formed and insulating the first and second metal layers. It is characterized in that a reflection layer for reflecting laser light is formed.

Further, in the method for processing a multilayer substrate according to the present invention, the insulating layer of the multilayer substrate is irradiated with a first laser beam.
A second laser beam whose optical axis coincides with the first laser beam is irradiated to a residue layer remaining on the metal layer below the insulating layer by the laser beam.

[0009]

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

FIG. 1 is a conceptual diagram showing a configuration of a processing apparatus for a multilayer printed circuit board according to an embodiment of the present invention. FIG. 1 shows laser oscillators 10 and 20 as first and second irradiation means having different wavelengths from each other, and mirrors 30 and 40 for changing the traveling direction of laser light emitted from the laser oscillators 10 and 20.
And a condensing lens 5 for collecting each laser beam whose traveling direction has been changed by the mirrors 30 and 40 on the multilayer printed circuit board 7.
0, 60 and a table 8 on which the multilayer printed circuit board 7 is placed
0 is shown.

FIG. 2 is a sectional view of the multilayer printed circuit board 7 according to the embodiment of the present invention. FIG. 2 shows an inner copper foil 3 electrically connected to an electronic component (not shown), a metal thin film 9 that is a reflection layer that reflects laser light, an insulating layer 1 made of a polymer that is an epoxy resin, and the like. The outer copper foil 2 and the hole 11 for forming a conductive layer are shown.

FIG. 3 to FIG. 6 are manufacturing process diagrams of the multilayer printed circuit board shown in FIG. The manufacturing process of the multilayer printed circuit board shown in FIG. 2 will be described with reference to FIGS.

First, as shown in FIG.
On the inner copper foil 3 having a thickness of m, a metal thin film 9 such as aluminum or rhodium is formed with a thickness of, for example, 1 μm. At this time, the metal thin film 9 may be formed by any method such as an evaporation method, a plating method, and a dipping method.

Subsequently, as shown in FIG.
Then, an adhesive sheet-like insulating layer 1 made of aluminum or the like having a thickness of, for example, 0.1 mm is adhered thereto.

Next, with the multilayer printed circuit board 7 placed on the table 80 such that the outer copper foil 2 is on the upper side, the table 80 is moved and the laser light emitted from the laser oscillators 10 and 20 respectively. Adjust the irradiation position of. Then, for example, a laser output of 1.5 W and a pulse width of 50 μs from the YAG (yag) laser of
Using harmonics, 30 shots in air, laser light 6
Is emitted.

The traveling direction of the emitted laser light 6 is changed by, for example, 90 degrees by the mirror 30. The laser beam 6 whose traveling direction has been changed enters the condenser lens 50.
The laser beam 6 incident on the condenser lens 50 irradiates the outer copper foil 2 and the insulating layer 1 of the multilayer printed circuit board 7 on the table 80 as shown in FIG.

Then, the outer layer copper foil 2 and the insulating layer 1 are removed by the laser beam 6, but at the same time, as shown in FIG. Carbon layer 111 remains. The carbon layer 111 reduces the contact area between a conductor such as solder and the inner copper foil 3 when attaching an electronic component or the like to the multilayer printed circuit board.
Removal is required.

Then, the excimer laser (KrF 248 nm) of the laser oscillator 20 is used for 10 mj, 300 mJ.
The visible laser light 6 is emitted at 3 Hz and 3 shots. Then, the traveling direction of the visible laser light 6 is changed by, for example, 90 degrees by the mirror 40. The visible laser light 6 whose traveling direction has been changed enters the condenser lens 60. The visible laser light 6 incident on the condenser lens 60 is applied to the carbon layer 111 remaining on the metal thin film 9 of the multilayer printed circuit board 7 on the table 80. Then, the carbon layer 111 becomes visible laser light 6
The hole 11 for forming the conductive layer is formed with a diameter of, for example, 0.05 mm.

As described above, using the processing apparatus shown in FIG.
Has been described above, but the manufacturing procedure is not limited to the above example, and laser beams may be simultaneously emitted from the laser oscillators 10 and 20, for example.

In this embodiment, the case where aluminum or rhodium is used for the metal thin film 9 has been described as an example.
The metal thin film 9 is not limited to the above materials and can be used as long as it has a high laser light reflectance and a small absorption coefficient. Further, since the reflectance and the like change depending on the wavelength of the laser light, the material that can be used for the metal thin film 9 also changes depending on the laser source.

For example, when the laser oscillator 1 is provided with a CO ₂ laser having a relatively long wavelength, the metal thin film 9 includes
Various materials such as gold, silver, copper, nickel, iron, and chromium can be used. The applicable material varies depending on the thickness of the metal thin film 9, the intensity of the laser beam, and the total irradiation amount, but the metal thin film 9 should be as thin as possible in order to keep the multilayer printed circuit board from becoming thick. For this reason, it is preferable to use a material having a reflectance of 80% or more.

[0022]

As described above, according to the present invention, a reflection layer is formed between an insulating layer and the first or second metal layer to reflect a laser beam irradiated to form a hole in the insulating layer. Therefore, even if the power of the laser beam is increased, the inner metal layer is not removed by the laser beam, and only the insulating layer can be removed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a processing apparatus for a multilayer printed board according to an embodiment of the present invention.

FIG. 2 is a sectional view of a multilayer printed circuit board 7 according to the embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of the multilayer printed circuit board shown in FIG. 2;

FIG. 4 is a manufacturing process diagram of the multilayer printed circuit board shown in FIG. 2;

FIG. 5 is a manufacturing process diagram of the multilayer printed circuit board shown in FIG. 2;

FIG. 6 is a manufacturing process diagram of the multilayer printed circuit board shown in FIG. 2;

FIG. 7 is a sectional view of a conventional multilayer printed circuit board.

FIG. 8 is a sectional view of a conventional multilayer printed circuit board.

FIG. 9 is a cross-sectional view of a conventional multilayer printed circuit board.

FIG. 10 is a sectional view of a conventional multilayer printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating layer 2 Outer layer copper foil 3 Inner layer copper foil 6 Laser beam 7 Multilayer printed circuit board 9 Metal thin film 11 Hole for forming conductive layer 10, 20 Laser oscillator 30, 40 Mirror 50, 60 Condenser lens 80 Table

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Claims (6)

[Claims] 1. A first and second metal layer electrically connected to a mounted electronic component, respectively, and an insulating layer formed between the first and second metal layers to insulate the first and second metal layers. Wherein a reflective layer is formed between the insulating layer and the first or second metal layer, the reflective layer reflecting a laser beam applied to form a hole in the insulating layer. Multi-layer board. 2. The multilayer substrate according to claim 1, wherein said reflection layer is made of gold, silver, copper, iron, aluminum or rhodium, and said laser light is a yag laser light. 3. The multilayer substrate according to claim 1, wherein the reflection layer is made of gold, silver, copper, iron, nickel, aluminum, rhodium or chromium, and the laser light is a CO ₂ laser light. 4. The method according to claim 1, wherein the reflection layer is formed by a vapor deposition method, a plating method, or a dipping method.
The multilayer substrate according to any one of claims 1 to 3, wherein 5. A residue layer remaining on a metal layer below the insulating layer by irradiating the insulating layer of the multilayer substrate according to claim 1 with a first laser beam, and the first laser beam. Irradiating a second laser beam whose optical axis coincides with the first laser beam. 6. The method according to claim 5, wherein the second laser beam is an ultraviolet laser beam.