JP3549932B2 - Exposure machine - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an exposure apparatus, and more particularly, to a structure such as a mask fixing portion for fixing a photomask.
[0002]
[Prior art]
In the initial stage of the image forming step in the manufacturing process of the printed wiring board, exposure and development are performed on the copper-clad laminate on which the dry film resist is stuck. In the exposure step, a photomask having a negative or positive pattern is brought into close contact with the copper-clad laminate. However, such a photomask is generally thin and difficult to handle. Further, the photomask needs to be arranged at an accurate position with respect to the copper-clad laminate. Therefore, when the exposure process is performed by the automatic exposure machine, it is necessary to securely fix the photomask to a predetermined portion.
[0003]
FIG. 4 shows an example of a conventional horizontal automatic exposure machine 30. In the case of this type of automatic exposure machine 30, a photomask 31 made of resin and in the form of a film is fixed to one side of a photomask fixture 32. The photomask fixture 32 is made of a transparent acrylic plate, and has a rectangular shape as a whole. Further, the photomask fixture 32 is attached to an upper portion of an attachment base 34 constituting the alignment stage 33. On the other hand, the copper-clad laminate 35 to be exposed is fixed to a resin suction plate 37 of a substrate holder 36 having a vacuum suction mechanism. In the exposure step, the photomask 31 and the copper-clad laminate 35 arranged opposite to each other are brought into close contact with each other after being aligned. Then, in this state, ultraviolet rays are irradiated from below the alignment stage 33 (that is, the surface side on which the photomask 31 is not attached). Then, the dry film resist (not shown) attached to the copper-clad laminate 35 is partially photopolymerized. Thereafter, through various steps such as development and etching, a desired image is finally formed on the copper-clad laminate 35.
[0004]
[Problems to be solved by the invention]
By the way, as shown in FIG. 4, a plurality of jig holes 38 for performing positioning or the like in another step may be formed on the outer edge of the copper-clad laminate 35.
[0005]
However, when the jig hole 38 is formed by punching or drilling, the opening is deformed, so that a projection 39 is likely to be formed at that portion. Therefore, in the step of bringing the copper-clad laminate 35 and the photomask 31 into close contact with each other, the state of contact particularly around the convex portion 39 deteriorates. For this reason, a gap is formed at the interface between the copper-clad laminate 35 and the photomask 31, and the accuracy of the image formed on the copper-clad laminate 35 deteriorates accordingly.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an exposure apparatus having excellent image forming accuracy.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is provided with a plurality of jig holes for positioning at an outer edge portion of a copper clad laminate coated with a photoresist as a substrate , In an exposure apparatus including a substrate holder for fixing the substrate having an opening portion of the jig hole that is a convex portion, and a mask fixing portion for fixing a photomask, at least the substrate in the mask fixing portion is provided. The gist of the present invention is an exposing machine in which a concave portion is formed at a position corresponding to the convex portion.
[0008]
According to a second aspect of the present invention, in the first aspect, a concave portion is formed at a position corresponding to the convex portion of the substrate in the substrate holder.
According to a third aspect of the present invention, in the first or second aspect, the recess is a non-through hole formed by boring.
[0009]
[Action]
According to the first to third aspects of the present invention, since the convex portion of the substrate enters the concave portion, the adhesion between the photomask and the substrate is improved, and a gap is hardly formed at the interface between the two.
[0010]
【Example】
Hereinafter, an embodiment in which the present invention is embodied in a horizontal automatic exposure machine will be described in detail with reference to FIGS.
[0011]
The horizontal type automatic exposure machine 1 of the present embodiment is an apparatus for automatically performing exposure while a substrate (specifically, a copper-clad laminate coated with a photoresist) 2 is horizontally fixed. FIG. 1 schematically shows a main part of the horizontal type automatic exposure machine 1. FIG. 2 shows the substrate holder 4, and FIG. 3 shows the alignment stage 3 as a mask fixing portion. A plurality of jig holes 2a are formed at the outer edge of the substrate 2. The opening of the jig hole 2a is a convex portion 2b.
[0012]
As shown in FIGS. 1 and 2, a rubber rubber seal 5 is provided on the bottom surface (that is, the substrate contact surface) S1 of the rectangular substrate holder 4. A rectangular fitting portion 6 is provided in a region inside the rubber rubber seal 5. An acrylic plate 7 as a flexible resin plate is fitted into the fitting portion 6. The acrylic plate 7 has several grooves (not shown) for evacuation along the vertical and horizontal directions. That is, a region corresponding to the size of the acrylic plate 7 is the suction area R2. A vacuum port 8 is formed between the rubber rubber seal 5 and the suction area R2. In this embodiment, four evacuation ports 8 are arranged at each corner. Each evacuation port 8 is connected to an electromagnetic valve 10 via a pipe 9. The electromagnetic valve 10 is connected to a vacuum pump (not shown). The substrate holder 4 as described above moves between the use position and the retracted position while holding the substrate 2.
[0013]
In the acrylic plate 7, a non-through hole 11 having a circular cross section as a concave portion is formed by counterboring at a position corresponding to the jig hole 2a of the substrate 2. The diameter of these non-through holes 11 is slightly larger (about 10 mm) than the diameter of the jig hole 2a. The depth of each non-through hole 11 is about 2 mm.
[0014]
As shown in FIGS. 1 and 3, a rectangular fitting portion 13 is formed on an upper portion of the mounting base 12 that forms the alignment stage 3. A transparent plate glass 14 as a photomask fixture is fitted into the fitting portion 13. The upper surface of the glass sheet 14 has a photomask contact surface S 2 for adhering the photomask 15.
[0015]
Examples of the sheet glass 14 used in this embodiment include the following. That is, (1) plate glass mainly containing silicic acid as an acidic component (eg, soda-lime glass, soda-lime aluminum glass, potassium lime glass, potassium lead glass); and (2) silicic acid and another acid as an acidic component at the same time. Glass having composition (for example, borosilicate crown glass, borosilicate flint glass), (3) glass using boric acid or phosphoric acid without using silicic acid as an acidic component (for example, boric acid flint glass, phosphate crown glass), and (4) Glasses using silicic acid as an acidic component and only alkalis as a basic component, (5) glass containing almost only silicic acid as a main component (for example, quartz glass), and (6) glass containing a rare element. The coefficient of thermal expansion of glass at a temperature lower than the glass transition point is about 2 × 10 ⁻⁶ / ° C. to 10 × 10 ⁻⁶ / ° C. in general, and the coefficient of thermal expansion of resin (generally 10 × 10 ⁻⁶ / ° C.) (A value somewhat larger than 10 ⁻⁶ / ° C.). Further, among them those listed above, for example, extremely small ^{(0.4 × 10 -6 /℃~0.5×10 -6 /} ℃ about) the thermal expansion coefficient, selecting the ▲ 5 ▼ quartz glass Is preferred. Further, (2) borosilicate crown glass and borosilicate flint glass (about 2 × 10 ⁻⁶ / ° C. to 5 × 10 ⁻⁶ / ° C.) are relatively preferable.
[0016]
Further, the thickness of the plate glass 14 is preferably about 5.0 mm. If the plate glass 14 is too thick, the loss of light energy when transmitting through the plate glass 14 may increase. On the other hand, if the sheet glass 14 is too thin, the above-mentioned problem is unlikely to occur, but the mechanical strength of the sheet glass 14 is impaired, so that the sheet glass 14 is easily broken.
[0017]
At the position corresponding to the jig hole 2a of the substrate 2 in the plate glass 14, as in the case of the acrylic plate 7, a non-through hole 16 having a circular cross section as a concave portion is formed by spot facing. These non-through holes 16 have a diameter of about 10 mm and a depth of about 2 mm. A through hole is formed at the center of the non-through hole 16 on the side of the plate glass 14. The pins of a pin cylinder arranged on the lower surface side of the glass sheet 14 are slidably inserted into these through holes. The tips of the pins also penetrate the photomask 15.
[0018]
In the horizontal automatic exposure machine 1 configured as described above, first, the substrate 2 transported is vacuum-adsorbed by the substrate holder 4. Next, the substrate holder 4 moves from the retracted position to the use position while the substrate 2 is vacuum-sucked. Therefore, after the alignment between the photomask 15 and the substrate 2 is performed, the distance between the substrate holder 4 and the alignment stage 3 is reduced. Next, evacuation is started by opening the electromagnetic valve 10. As a result, air is exhausted from the evacuated space defined by the substrate holder 4, the plate glass 14, and the rubber rubber seal 5, and the pressure in the space gradually decreases. Then, finally, the substrate 2 and the photomask 15 come into close contact with each other. After reaching this state, parallel light is emitted from exposure means (not shown) arranged below the plate glass 14. Then, of the dry film resists (not shown) adhered to both surfaces of the substrate 2, those on the surface side that has received the parallel light are partially photopolymerized.
[0019]
When the electromagnetic valve 10 is closed after the exposure is completed, the degree of vacuum in the evacuation space is reduced, and the plate glass 14 is easily separated from the substrate holder 4. Thereafter, the substrate holder 4 returns from the use position to the retracted position. The substrate 2 that has undergone the exposure process is carried out of the horizontal automatic exposure machine 1, and then undergoes a development process, an etching process, and the like. As a result, a desired image is finally formed on the substrate 2.
[0020]
By the way, in the horizontal automatic exposure machine 1 of the present embodiment, the non-through holes 11 and 16 are formed in both the plate glass 14 and the acrylic plate 7 at positions corresponding to the convex portions 2b of the substrate 2. Therefore, when the substrate 2 and the photomask 15 are brought into close contact with each other, the convex portions 2b enter the concave portions 11 and 16, and are not affected by the convex portions 2b. For this reason, the adhesion between the photomask 15 and the substrate 2 is improved, and a gap is hardly formed at the interface between the two. That is, it becomes difficult for the substrate 2 to float from the photomask 15. Therefore, the image forming accuracy is reliably improved as compared with the related art.
[0021]
In the case of this embodiment, the photomask 15 is fixed to the photomask contact surface S2 existing on the plate glass 14, and the substrate 2 is fixed to the substrate contact surface S1 existing on the acrylic plate 7. . With this configuration, even if the evacuation in the evacuation space is performed, no physical change such as bending of the plate glass 14 occurs. On the other hand, the flexible acrylic plate 7 bends. Therefore, when vacuuming is performed, first, the central portion of the acrylic plate 7 comes into close contact with the upper surface of the substrate 2. Such close contact extends from the central part of the substrate 2 to the peripheral part. Along with this, the air in the evacuation space is discharged smoothly and reliably. Therefore, even if the time required for evacuation is short, there is no unevenness in evacuation, and the photomask 15 and the substrate 2 can be completely adhered. This has a positive effect on improving image forming accuracy.
[0022]
Further, in the horizontal automatic exposure machine 1, a photomask 15 is fixed on a plate glass 14 having a sufficiently small thermal expansion coefficient. That is, even if the temperature rises due to the heat of the exposure means, the degree of elongation of the sheet glass 14 is extremely smaller than that of the resin, and the photomask 15 is less likely to be displaced. Therefore, this also has a positive effect on improving the image forming accuracy.
[0023]
The present invention can be modified as follows, for example.
(1) Instead of the acrylic plate 7 used in the embodiment, for example, a plate material such as vinyl chloride, glass epoxy resin, and aluminum may be used.
[0024]
(2) Instead of the embodiment in which the concave portions 11 and 16 are provided in both the plate glass 14 and the acrylic plate 7, a configuration in which the concave portions 16 are provided only on the plate glass 14 side may be adopted.
(3) It is of course possible to form the recesses 11 and 16 by a method other than counterboring (for example, after forming a through hole and closing the hole).
[0025]
(4) The shape of the concave portions 11 and 16 is arbitrary, and may be, for example, a groove shape or the like.
(5) The present invention can be applied to a vertical double-sided automatic exposure machine or the like, or to other non-automatic exposure machines.
[0026]
Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiment and other examples are listed below together with their effects.
(1) In claim 3, the non-through hole is a non-through hole slightly larger than the convex portion. With this configuration, image forming accuracy is further improved.
[0027]
The technical terms used in this specification are defined as follows.
"Photomask: Refers to a thin plate material having a negative or positive pattern used in the image forming process of a printed wiring board."
[0028]
【The invention's effect】
As described in detail above, according to the first to third aspects of the present invention, the adhesion between the substrate and the photomask is improved, so that the image forming accuracy can be reliably improved. According to the second aspect of the present invention, since the concave portion is provided not only in the mask fixture but also in the substrate holder, it is possible to more reliably improve the image forming accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a horizontal type automatic exposure machine in an embodiment.
FIG. 2 is a schematic bottom view of the substrate holder.
FIG. 3 is a schematic plan view of an alignment stage.
FIG. 4 is a schematic sectional view of a conventional horizontal automatic exposure machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... (Horizontal type automatic) exposure machine, 2 ... Substrate, 2b ... Opening of the jig hole as a convex part, 3 ... Alignment stage as a mask fixing part, 4 ... Substrate holder, 11, 16 Through-hole, 15 ... Photomask.

Claims (3)

A plurality of jig holes for positioning are formed at the outer edge of the copper-clad laminate coated with a photoresist as a substrate , and the substrate in which the opening of the jig hole is a projection is fixed. An exposing machine comprising: a substrate holder for fixing a photomask; and a concave portion formed at least at a position corresponding to the convex portion of the substrate in the mask fixing portion. 2. The exposure apparatus according to claim 1, wherein a concave portion is formed at a position corresponding to the convex portion of the substrate in the substrate holder. The exposure apparatus according to claim 1, wherein the recess is a non-through hole formed by counterboring.

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