JP2003236689A - Method of drilling ceramic green sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of drilling a ceramic green sheet capable of reducing the electric resistance of a metal paste within a via hole for connecting upper and lower electric circuit wiring to each other. <P>SOLUTION: The sectional shape of a laser beam is faired by a mask having a through-hole of a square shape. The laser beam faired by the mask is made incident on the ceramic green sheet by an imaging optical system for imaging the through-hole of the mask onto the front surface of the ceramic green sheet, by which a hole is formed in the incident position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for making holes in a ceramic green sheet, and more particularly to a method for making holes in a ceramic green sheet by making a laser beam incident thereon.

[0002]

2. Description of the Related Art In the process of manufacturing high density multilayer chip inductors and LC filters, there is a process of making holes in a ceramic green sheet. The green sheet is formed of a ceramic material before firing, and is produced by applying a ceramic material on a resin carrier sheet.

When a carbon dioxide laser beam is incident on the green sheet, a substantially circular through hole (via hole) is formed at the incident position. A metal paste is filled in the via hole, and electric circuit wiring is printed on the surface of the green sheet. By laminating the green sheets, a chip inductor or the like is manufactured. The metal paste filled in the via holes electrically connects the upper and lower electric circuit wirings.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for punching a ceramic green sheet capable of reducing the electric resistance of a metal paste in a via hole which connects upper and lower electric circuit wirings to each other. Is.

[0005]

According to one aspect of the present invention, the step of shaping the cross-sectional shape of a laser beam with a mask having a rectangular through hole, and the through hole of the mask on the surface of a ceramic green sheet. The method for forming a hole in a ceramic green sheet, which comprises: forming a hole in the position where the laser beam shaped by the mask is incident on the ceramic green sheet by an imaging optical system for forming an image on the ceramic green sheet.

Since an image of a rectangular through hole is formed on the ceramic green sheet, it is possible to make a hole having a shape close to a square.

[0007]

1 is a schematic view of a laser processing apparatus according to an embodiment of the present invention. The laser light source 1 emits a pulsed laser beam. The laser light source 1 is, for example, a carbon dioxide laser oscillator, and its oscillation wavelength is about 10 μm. The pulse laser beam emitted from the laser light source 1 is expanded in beam diameter by the beam expander 2,
It is incident on the mask 3.

The mask 3 is provided with a rectangular, for example, square or rectangular through hole. The pulse laser beam that has passed through this through hole is reflected by the folding mirror 4 and enters the field lens 5. The laser beam focused by the field lens 5 enters the galvano scanner 6. The galvano scanner 6 scans the incident pulsed laser beam in a two-dimensional direction.

The scanned pulse laser beam is converged by the fθ lens 7 and is incident on the ceramic green sheet 20 held on the XY stage 8. The condensing optical system including the field lens 5 and the fθ lens 7 forms an image of the through hole of the mask 3 on the surface of the green sheet 20. The imaging magnification is, for example, 10 to 20 times.

By scanning the laser beam with the galvano scanner 6, the image forming position of the through hole of the mask 3 can be moved within a certain area on the surface of the green sheet 20. An area in which the imaging position can be moved by the galvano scanner 6 is referred to as a unit processing area. When all the drilling operations in one unit processing area are completed, the XY stage 8 is driven to move the green sheet 20, so that the drilling operations in the other unit processing area can be performed.

Since the through holes of the mask 3 are rectangular, the image formed on the surface of the green sheet 20 is also rectangular. Therefore, a substantially rectangular hole is formed in the green sheet. For example, the through hole of the mask 3 has a side length of 3 mm.
When the imaging magnification is 1/20, the length of one side of the hole formed in the green sheet is approximately 150 μm.
It becomes m.

2A to 2D are plan views of the green sheets of the first to fourth layers to be laminated. 2A to 2D show only a portion corresponding to one chip inductor. At the time of punching, the green sheet is not separated for each chip inductor.

As shown in FIGS. 2 (A) to 2 (D), on the first to fourth layers of green sheets, three sides other than the lower side and three sides other than the left side of each square of the outer periphery of the square are respectively included. Wirings 30, 32, 3 along the three sides other than the upper side and the three sides other than the right side
4 and 36 are printed. Square via holes 31, 33, 3 are provided at the lower left end of the wiring 30, the upper left end of the wiring 32, the upper right end of the wiring 34, and the lower right end of the wiring 36, respectively.
4 and 36 are formed.

The wiring 30 formed on the first-layer green sheet is adhered underneath via the metal paste embedded in the via hole 31, and the lower left of the wiring 32 formed on the second-layer green sheet. Connected to the end. Similarly, the wiring 3 formed on the second-layer green sheet
2 is the wiring 3 formed on the green sheet of the third layer
The wiring 34 is connected to the upper left end of the wiring 4, and the wiring 34 is connected to the upper right end of the wiring 36 formed on the green sheet of the fourth layer. In this way, the wires 30, 32, 34, and 36
An inductor composed of is obtained. Wiring 30, 32,
The widths of 34 and 36 are all equal.

FIG. 2E shows a perspective view of a portion where the via hole 31 is formed. A square pole having a square planar shape penetrates the green sheet. Other beer holes 3
The shapes of 3, 35, and 37 are also the same as the shape of the via hole 31. The via holes 31, 33, 35, and 37
The length of one side of the square cross section of the wirings 30, 32, 34,
And the width of 36.

FIG. 2F is a perspective view of the via hole 40 formed by the conventional laser processing method. The plane shape of the via hole 40 is circular. The diameter of the circular cross section of the via hole is almost equal to the width of the wiring formed on the green sheet.

FIG. 3 shows plan views of via holes having a square cross section and a circular cross section. Since the length of one side of the square cross section 45 and the diameter of the circular cross section 46 are both equal to the wiring width, the circular cross section 46 is inscribed in the square cross section 45. Therefore, the cross-sectional area of the square cross-section via hole is larger than the cross-sectional area of the circular cross-section via hole. Assuming that the thickness of the green sheet and the specific resistance of the metal paste embedded in the via hole are equal, making the cross section of the via hole square makes it possible to reduce the electrical resistance of the metal paste embedded in the via hole.

Even if the spot of the laser beam formed on the surface of the green sheet is square, the cross section of the via hole actually formed has four square corners as shown by the solid line 47 in FIG. It has a rounded shape. More specifically, the outer circumference of the cross section indicated by the solid line 47 passes between the outer circumference of the square and the circumference inscribed therein.

Although the via hole has a square cross section in the above embodiment, it may have a rectangular shape instead of a square shape.
However, in reality, the four corners of the rectangle are rounded. In this case, the outer periphery of the cross section of the via hole passes between the rectangle and the outer periphery of the ellipse inscribed therein.

In the above embodiment, the cross-sectional shape of the via hole to be formed can be easily changed by replacing the mask 3. Further, even if the arrangement pattern of the via holes on the green sheet is changed, the incident position of the laser beam can be easily changed by controlling the galvano scanner 6.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0022]

As described above, according to the present invention,
The cross-sectional shape of the hole formed in the ceramic green sheet can be approximated to a square. This makes it possible to reduce the resistance of the electric circuit configured by laminating the ceramic green sheets.

[Brief description of drawings]

FIG. 1 is a schematic view of a laser processing apparatus used in an embodiment of the present invention.

2A to 2D are plan views of respective layers of a chip inductor, FIG. 2E is a perspective view of a via hole manufactured by a method according to an example, and FIG. 2F is a conventional method. FIG. 6 is a perspective view of a via hole manufactured in Step 1.

FIG. 3 is a diagram showing a relationship between a square cross section, a circular cross section, and a cross section of an actually formed via hole.

[Explanation of symbols]

1 laser light source 2 beam expander 3 masks 4 folding mirror 5 field lens 6 galvano scanner 7 fθ lens 8 XY stage 20 green sheets 30, 32, 34, 36 wiring 31, 33, 35, 37, 40 Via holes 45 square cross section 46 circular cross section 47 Cross section of via hole actually formed

Claims (2)

[Claims] 1. A mask for shaping the cross-sectional shape of a laser beam with a mask having a rectangular through hole, and an imaging optical system for forming an image of the through hole of the mask on the surface of a ceramic green sheet. A step of making a laser beam shaped by the method incident on the ceramic green sheet, and forming a hole at the incident position. 2. The ceramic according to claim 1, further comprising the step of moving the image of the through hole of the mask on the surface of the ceramic green sheet by scanning with a laser beam to form a plurality of holes. How to drill a green sheet.