JPH04356392A - Optical processor - Google Patents

Abstract

PURPOSE:To improve the utilization efficiency of light, in the optical processor for executing viahole working, etc., to, for instance, a copper polyimide base plate by a laser light by using a mask for a transfer. CONSTITUTION:Working is executed by providing a Fresnel band plate 12 as a condensing means on four pieces of circular light propagating parts 11 provided on a mask 2, and condensing a laser light 1 radiated to the mask 2 to a printed board 7. Since light is condensed by the Fresnel band plate 12, the utilization efficiency of light can be improved.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention is a method of forming via holes in a printed circuit board by laser light using a mask, for example.
This invention relates to an optical processing device that processes holes, etc.

0002

[Prior Art] FIGS. 6 and 7 are, for example, Japanese Patent Laid-Open No. 63-22
This figure shows a laser processing apparatus which is a conventional optical processing apparatus disclosed in Japanese Patent No. 0991, and FIG. 6 is a block diagram showing the optical processing section of the apparatus, and FIG. 7 is a plan view of a mask.

In these figures, 1 is a laser beam emitted from a light source (not shown), and has a wavelength of 248 nm.
] KrF excimer laser light is used. Reference numeral 2 denotes a mask as a light shielding member, and as shown in FIG. 7, a light transmitting portion 4 for transmitting light as a light propagating portion is provided with a predetermined shape on a light transmitting plate 3 made of synthetic quartz for transmitting light. A light blocking portion 5 that blocks light is formed of a thin film so as to constitute a light transmitting plate 3, and the light is transmitted through the light transmitting plate 3 (hereinafter referred to as "transmission" and "propagation").

Note that in FIG. 7, the light passing section 4 is shown as having a continuous shape for convenience of illustration, but to be more precise, the light passing section 11 has a diameter of about 20 [μm] (see FIG. 1).
(see) are arranged in a pattern similar to the light passing portions 4 in FIG. 7, with about 100 pieces scattered per square centimeter. Therefore, the aperture ratio of the mask 2 (the ratio of the area of the light passage section 4 to the area of the entire mask 2) is about 0.03%. 6 is an imaging lens having a focal length f, and is provided at a distance A from the mask 2. Reference numeral 7 denotes a printed circuit board made of polyimide, which is an object to be processed, and is provided at a distance B from the imaging lens 6.

Next, the operation will be explained. The laser beam 1 is irradiated onto the mask 2, and the laser beam 1 passes only through the light passage section 4. After that, the laser beam 1 enters the imaging lens 6, and when the following relational expression 1/A+1/B=1/f holds between the distances between the imaging lens 6, the mask 2, and the printed circuit board 7, The shape of the light passing portion 4 of the mask 2 is projected onto the printed circuit board 7 in an inverted form, and the via hole 8 is processed on the printed circuit board 7 according to the shape. At this time, the magnification of the projected image corresponding to the shape of the light passing portion 4 of the mask 2 is B/A. In addition, the aperture ratio of mask 2 is 0.03
The remaining 99.97% of the light is absorbed or reflected by the mask 2.

[0006]

[Problems to be Solved by the Invention] Since the conventional laser processing apparatus is constructed as described above, most of the laser beam 1 irradiated onto the mask 2 is reflected or absorbed by the mask 2, and the energy of the laser beam is reduced. is almost (9 in the conventional example above)
There was a problem that 9.97%) of the light was not used for processing and was lost, resulting in low light utilization efficiency. This invention was made to solve the above-mentioned problems, and an object of the invention is to obtain a light processing device with high light utilization efficiency.

[0007]

[Means for Solving the Problems] The optical processing apparatus according to the present invention is such that a light condensing means is provided at or near the light propagation section of a light shielding member to condense light onto a workpiece.

[0008]

[Operation] In the present invention, the area of the light passing portion is increased, and the light is focused by the light focusing means and applied to the object to be processed. As a result, the intensity of the light irradiated onto the workpiece can be increased, and the
Improves light usage efficiency.

[0009]

[Embodiment] Figs. 1 and 2 show an embodiment of the present invention. Fig. 1 is a perspective view showing an optical processing section of a laser processing device, and Fig. 2 is a plan view showing details of a Fresnel strip. . In these figures, reference numeral 11 denotes a circular light propagation section provided in the light shielding section 5 so that light can pass therethrough.In this embodiment, for convenience of illustration, the light passage section is divided into four light propagation sections 11. However, the light passage section 4 shown in FIG. 7 is one in which a large number of light propagation sections 11 are arranged in a predetermined shape. Reference numeral 12 denotes a circular Fresnel band plate which is a condensing means provided in the light propagation section 11, and a ring-shaped light passing band 13 for passing light and a ring-shaped light blocking band 14 for blocking light are arranged alternately. It is provided. The boundaries of each light passing zone 13 and light blocking zone 14 are a1(2m+1)1/2 (m=
0, 1, 2, ...) (a1: Fresnel strip parameter, described later).

Next, the operation will be explained using FIGS. 1 and 2, FIG. 3 which is a light distribution diagram, and FIG. 4 which is an explanatory diagram of condensing light. In FIG. 1, when a laser beam 1 consisting of a plane wave is irradiated onto a mask 2 provided with a Fresnel strip 12, the laser beam 1 is diffracted by each Fresnel strip 12 and reaches a printed circuit board 7 for processing. Since the Fresnel band plate 12 has the dimensions described above, the distribution of light passing through the light passing band 13 has the distribution shown in FIG. The light is condensed at the condensing point F, and a higher intensity of light on the mask 2 is obtained. At this time, the relationship between the distance f (focal length) to the condensing point F and the parameter a1 of the Fresnel band plate is given by (a1)2=λ·f (λ: wavelength of the laser beam 1).

[0011] Furthermore, the intensity I of the light at the condensing point F is given by I=m2, where I0 is the intensity on the mask 2 surface.
It is given by I0 (m: number of Fresnel bands). Normally, the number of Fresnel bands (light passing band 13) is about 6 to 10, so by substituting that value into the above equation, the intensity I of the light at the focal point F is equal to the intensity I0 of the light on the mask 2. This results in a gain of 36 to 100 times. Of course, in this embodiment, since four Fresnel strip plates 12 are provided, holes can be drilled at four distant locations at the same time, as in the conventional transfer optical system.

[0012] Here, the size of the Fresnel strip 12 is calculated. The wavelength of light is λ=248 [mm], and the focal length is f=
If it is 50 [mm], a1=111 [μm]. When the number of Fresnel bands is m=10, the diameter of the Fresnel band plate 12 is a1(2m+1)1/2=509 [μm]. Therefore, in this case, the distance between the holes you want to machine is 509
It would be better if it was larger than [μm].

In the embodiment shown in FIG. 1, an example was shown in which the light emitted from the Fresnel strip 12 is directly irradiated onto the printed circuit board 7, but as shown in FIG. A configuration may also be adopted in which the light distribution is transferred to the printed circuit board 7 by the lens 22.

Furthermore, since the pattern of the Fresnel strip 12 in FIG. 1 has the configuration shown in FIG.
(r), where the radius is r, the Fresnel number is N, and the distance to the outermost edge of the Fresnel strip is D, I=c・{J1(2Nπr/D)/(Nπr/D)}2
(c: constant of proportionality) However, by using other shapes of Fresnel strip patterns, the distribution of light at the focal point can be made closer to a rectangle or ring-shaped. . A slit-like light distribution can also be obtained by using a one-dimensional Fresnel strip pattern. Note that the same effect can be achieved even when using other light condensing means such as a microlens instead of the Fresnel strip.

In each of the above embodiments, the mask 2 is shown as the light shielding member, but it may also be a resicle, an aperture, etc. Alternatively, instead of using a light transmitting plate, for example, a through hole of a predetermined shape may be formed in a thin metal plate. A hole may be formed to form a light propagation section, and a light condensing means may be provided here. Further, the light condensing means may be provided near the light propagation section. Furthermore, the light is not limited to laser light; other light can have similar effects, and the light processing device is capable of ablation (a) using laser light.
The optical processing apparatus is not limited to processing (blation), and may be other optical processing equipment such as one that performs other processing or an exposure equipment in photolithography.

[0016]

As described above, according to the present invention, since the light condensing means for concentrating light on or near the light propagation part of the light shielding member is provided, the light irradiated onto the light shielding member can be effectively used. Available.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a laser processing apparatus which is an embodiment of the present invention.

FIG. 2 is a plan view of a Fresnel strip showing an embodiment of the present invention.

FIG. 3 is a light distribution diagram showing the distribution of light propagating through a Fresnel strip in an embodiment of the present invention.

FIG. 4 is an explanatory diagram of light collection in an embodiment of the present invention.

FIG. 5 is a perspective view showing another embodiment of the invention.

FIG. 6 is a configuration diagram showing an optical processing section of a conventional laser processing device.

FIG. 7 is a plan view of a conventional light shielding member.

[Explanation of symbols]

1 Laser light 2. Mask 5. Light shielding part 7 Printed circuit board 11 Light shielding member 12 Fresnel strip 21 Light condensing surface 22 Lens

Claims (1)

[Claims] 1. A light processing apparatus that processes a workpiece with the light propagated through the light propagation part, the apparatus comprising a light shielding member having a predetermined shape and provided with a light propagation part for propagating light,
An optical processing apparatus characterized in that the light propagation section is provided with a condensing means for condensing the light onto the object to be processed.