JPS6214494A - Ultraviolet laser irradiation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the application of ultraviolet rays from an ultraviolet laser to a circuit pattern mask formed on a transparent film, etc. ! ! This relates to an ultraviolet laser irradiation method in an exposure device or the like that irradiates a hardening resist to print a circuit pattern formed on a mask, and is used in fields where it is necessary to form fine images.

2. Description of the Related Art In the production of printed circuit boards, circuit patterns tend to become finer, and it is necessary to increase the resolution of exposure equipment.

In order to expose and print a fine circuit pattern formed on a mask onto a printed circuit board coated with a resist such as an ultraviolet curing etching resist or solder resist, parallel light is required from the viewpoint of resolution. An irradiation method has been proposed in which pseudo-parallel light is created by combining an ultra-high pressure discharge lamp close to the light source and an optical system.

FIG. 2 shows an example of a conventional irradiation method of this type of exposure apparatus. In the figure, 6 is an ultra-high pressure discharge lamp such as an ultra-high pressure mercury lamp, 7 is an ellipsoidal mirror, 8 is a primary reflector, 9 is an inch grater, 10 is a secondary reflector, and 11 is a circuit pattern formed. The mask 12 is a printed circuit board coated with resist. The ultraviolet light from the ultra-high pressure discharge lamp 6 is focused on the primary reflecting mirror 8 via the elliptical surface 17, the light is reflected by changing its direction by approximately 90 degrees, and transmitted through the inch grater 9. The secondary reflecting mirror 10 is irradiated with light. The second reflection vA10 is installed at an angle of approximately 45 degrees with respect to the printed circuit board 12, and the light reflected by the second reflection vA10 is directed to the entire surface of the printed circuit board 12 through the mask 11. The circuit pattern of the mask 11 is printed onto the resist coated on the printed circuit board 12. A cold mirror is used as the second O4 mirror 8 to absorb heat rays from the ultra-high pressure discharge lamp 6. The inch grater 9 is constructed by combining small convex lenses made of quartz to improve the transmittance of ultraviolet rays.

Problems to be Solved by the Invention Since the exposure time for printing the number of irradiated objects such as printed circuit boards is determined by the minimum value of the ultraviolet intensity of the irradiated object, it is necessary to uniformly irradiate the object with as high a value as possible. is necessary. However, in the conventional method described above, the degree of uniformity is improved by devising a part of the inch grater and a reflector at the final stage, but since the ultraviolet rays emitted from a part of the inch grater are spread out, what can be done? The distribution of ultraviolet light intensity is higher at the center than at the edges. In order to improve uniformity, there are methods such as increasing the optical path length or increasing the irradiation area relative to the size of the object to be irradiated, but either method reduces the UV intensity and increases the exposure time. There was a problem. In addition, as a measure to improve parallelism, there are methods such as making the final stage anti-RF4ILI a parabolic mirror, but if the finish of the parabolic mirror is incomplete, the parallelism will deteriorate in some parts, and the printing A problem arises in that the quality of products such as substrates is affected.

Moreover, using a high-quality parabolic mirror causes problems such as an extremely high price. Furthermore, parallelism can be improved by increasing the optical path length, but similar to the case of uniformity, the problem arises that the ultraviolet intensity decreases and the exposure time becomes longer.

The present invention provides a method for irradiating ultraviolet rays in an exposure apparatus that solves the above-mentioned problems.

In order to solve the problem, the present invention uses an ultraviolet laser, which is a collimated light source, as a light source, and a polyhedral reflector that rotates the ultraviolet rays from the ultraviolet laser in order to obtain good parallelism. Rather than scanning with a mirror, etc., scan two opposing mirrors at a right angle. By moving each one in relation to each other, the ultraviolet rays from the ultraviolet laser can be effectively irradiated onto the fixed object to be irradiated, such as a printed circuit board, and the object to be irradiated can be uniformly irradiated with highly parallel ultraviolet rays from the ultraviolet laser. This is how it was done.

Function: The primary reflector, which has an area larger than the spot diameter of the ultraviolet rays from the ultraviolet laser, receives the ultraviolet rays from the ultraviolet laser, and reflects the ultraviolet rays horizontally by 90 degrees to the irradiated surface. Next, the ultraviolet rays reflected by this primary reflecting mirror are placed on the same plane as the primary reflecting mirror and facing the primary reflecting mirror at an angle of 45 degrees to the irradiated object. is,
In addition, the ultraviolet rays from the ultraviolet laser are received by a rectangular primary reflecting mirror whose width is larger than the spot diameter of the ultraviolet rays and whose length is longer than the object to be irradiated, and the ultraviolet rays from the ultraviolet laser are reflected by changing the direction 90 degrees in the vertical direction. Irradiates the object to be irradiated.

Furthermore, the primary reflecting mirror is continuously moved back and forth in the same direction as the incident optical axis from the ultraviolet laser, and the secondary reflecting mirror is moved back and forth in the same direction as the incident optical axis from the ultraviolet laser. By moving in the optical axis direction of the reflected light from y4#A, that is, by moving the first-order anti-fJ4 mirror and the second-order reflecting mirror in a perpendicular positional relationship,
The entire surface of a fixed object to be irradiated can be uniformly irradiated with highly parallel ultraviolet rays emitted from an ultraviolet laser.

Example An embodiment of the present invention will be described below with reference to FIG.

In the figure, 1 is the ultraviolet laser, 2 is the primary reflector that changes the direction of the incident light from the ultraviolet laser by 90 degrees and reflects it horizontally, and 3 is the primary reflection! a secondary reflecting mirror that changes the direction of 90a in the vertical direction and reflects the reflected light from f12;
4 is a mask depicting a circuit for a printed circuit board, and 5 is a printed circuit board coated with resist. The primary reflecting mirror 2 and the secondary reflecting mirror 3 are arranged above the mask 4, and the primary reflecting mirror 2 is inclined at 45 degrees with respect to the incident light C from the ultraviolet laser 1. The light source is installed in the same direction as the incident light C, and moves back and forth continuously in the A-A direction, which is the same direction as the incident light C.

The secondary reflecting mirror 3 is installed with an inclination of 45 degrees with respect to the mask 4, and while reflecting the reflected light from the second stage 04&l12 by changing the direction of the reflected light by 90 degrees in the vertical direction, the primary reflecting mirror 3 It moves in the B-B direction, which is the same direction as the reflected light from &lt2. The size of the primary reflector 2 is the ultraviolet laser 1
The size of the secondary reflecting mirror 3 is a rectangle whose width is slightly larger than the spot diameter of the ultraviolet rays and whose length is larger than the width of the object to be irradiated.

In this embodiment of the present invention, the ultraviolet C emitted from the ultraviolet laser 1 is the second stage o4! The light is turned 90 degrees horizontally by the li2 and reflected onto the secondary reflecting mirror 3, and further reflected by the secondary reflecting mirror 3 by turning 90 degrees vertically downward to illuminate the mask 4. The printed circuit board 5 is irradiated in the form of a spot through the beam. By moving the primary reflecting mirror 2 in the direction from A to A, the spot of ultraviolet rays irradiates the mask 4 in a band shape while moving in the direction from a to a. When the ultraviolet ray spot reaches the end in the a direction, the secondary reflecting mirror 3 is moved to 8 with a width slightly smaller than the ultraviolet ray spot diameter.
, and move the primary reflection &l12 from A to B' direction.
By moving the spot from a to the direction A, the spot on the mask 4 moves from a to the direction a, and the spot is irradiated in a band shape again. By repeating this state, the spot band becomes b
, and moves from the direction b to the printed circuit board 5 through the mask 4.
The circuit pattern drawn on the mask 4 can be printed onto the mask 4.

Further, by giving the mirror finish of the primary reflecting mirror 2 and the second stage 04$13 a finish that matches the wavelength of ultraviolet rays, it is possible to efficiently reflect the ultraviolet rays. Also, whether the mask 4 and the printed circuit board 5 coated with resist are in close contact or not,
Since the ultraviolet laser is a high-quality collimated beam, it produces high-resolution printing.

Further, by arranging the same configuration above and below the printed circuit board 5, double-sided exposure can be performed.

The irradiation method of the present invention can be applied not only to printing circuit patterns on printed circuit boards but also to forming fine images on screen printing boards, etching, and the like.

Effects of the Invention By using the ultraviolet laser irradiation method according to the present invention as described above, it is possible to directly utilize the parallel beams that characterize ultraviolet lasers, obtain highly parallel beams, improve resolution, and improve the precision of fine circuits. It is easier to manufacture printed circuit boards, etc., and the surface to be irradiated can be uniformly irradiated, resulting in high-quality images.The powerful ultraviolet rays from the ultraviolet laser can speed up the printing speed, shortening the exposure time. The practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a three-dimensional view showing an embodiment of the ultraviolet laser irradiation method of the present invention, and FIG. 2 is a sectional view showing an example of the conventional irradiation method.

Claims (1)

[Claims] In an ultraviolet laser irradiation method in an exposure device that irradiates ultraviolet rays from an ultraviolet laser, two
An ultraviolet laser irradiation method that uniformly irradiates the irradiated object without moving it by moving two reflecting mirrors in a perpendicular relationship.