JPS6381331A - Holding method for mask film in exposing device - Google Patents

Abstract

PURPOSE:To prevent occurrence of positional deviation of a mask film by holding the mask film to a printing frame by means of charge attraction. CONSTITUTION:When positioning with a work is determined, DC voltage is applied to a mask film 4 closely contacted to circuit patterns 1a, 1b formed by ITO film of a printing frame 1 by a power source 2. Negative charge is charged on the surface of the pattern 1a of the ITO film by applied voltage, and plus charge is charged on the surface of the pattern 1b. As polyethylene terephtalate, a high dielectric, is used for the mask film 4, the surface of the mask film 4 is charged and attracted to the printing frame 1 by attraction between charge. Thus, positional deviation of the mask film does not occur, mask film of various size can be handled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for attaching a mask film to a printing frame of an exposure apparatus, and more particularly to a method for holding a mask film by electrostatic attraction.

[Conventional technology]

In the manufacturing process of printed circuit boards, etc., raw boards (workpieces)
When exposing and printing an original image, it is necessary to bring the original image film or the like into close contact with a workpiece such as a printed circuit board in order to perform accurate exposure. Precisely maintaining the mutual positional relationship between the original original image film (hereinafter referred to as mask film) and the workpiece is one of the most important control points in exposure printing.
Similarly, it is necessary to firmly hold the mask film in close contact with the printing frame without shifting the position.

FIG. 3 shows a conventional method for holding a mask film in an exposure and printing frame, and will be described below with reference to the drawings. In the figure, the exposure and printing frame includes a lower frame (pedestal) 104, an upper frame 101, a mask film 102, a workpiece 103, a vacuum forming rubber 105 attached to the periphery of the upper frame 101, and a vacuum suction port 10.
6.107. A transparent resin plate or glass plate is used for the upper frame 101, and the mask film 102 is sucked into the upper frame 101 by suction from a vacuum suction port 106 using a vacuum pump (not shown) or the like. From the vacuum suction port 106, a narrow suction groove 106a is formed in a shape and position that does not affect exposure.
, 106b, and 106c are engraved to make the mask film 102 come into close contact with the upper frame 101. Thereafter, the upper frame 101 descends and comes into close contact with the workpiece 103 transferred to the lower frame (pedestal) 104, and suction is applied from the vacuum suction port 107 to remove the workpiece 103 surrounded by the vacuum forming rubber 105 and the mask film 102. This was to allow them to adhere more tightly and maintain their mutual positional relationship precisely. Father frame.

Even in a double-sided exposure device that exposes both sides of the lower frame simultaneously, the mask film is attached and held to the lower frame in the same manner as described above.

[Problem that the invention seeks to solve]

The method of attaching and holding the mask film to the printing frame according to the above-mentioned conventional technique uses a mechanical means called vacuum suction, and problems that need to be improved have been identified.

Firstly, since the mask film is vacuum-adsorbed using a vacuum pump, etc., the upper frame of the printing frame is damaged.

During the main vacuum suction, which creates a vacuum between the lower frames to firmly adhere the mask film and the workpiece, there is a risk that the balance with the vacuum suction of the mask film on the upper frame may be lost, causing the mask film to shift. Second, it is difficult to maintain good vacuum suction of the mask film unless you use a printing frame that corresponds to the shape and dimensions of the mask film. The printing frame had to be replaced every time the mask film was replaced. Thirdly, it was necessary to carve thin grooves for vacuum suction for adsorbing the mask film in a shape and position that would not affect exposure, which required extra man-hours.

The present invention was created to solve the above problems, and there is no risk of misalignment of the mask film.
It is an object of the present invention to provide a method for holding a mask film that is versatile enough to support mask films of various sizes and has excellent operability.

[Means for solving problems]

A specific means to solve the above problem is to create a circuit pattern using a transparent conductive thin film on a translucent plate that serves as the printing frame of the exposure device, and then apply a voltage to the mask film to charge and attract the mask film. The method of retention is as follows.

[Effect]

By using the above-described mask film holding method, a voltage is applied to a circuit pattern made of a conductive transparent thin film formed on a translucent plate that serves as a printing frame of an exposure device. The circuit pattern becomes electrically charged when a voltage is applied, and the thin, lightweight mask film is held by the electrically charged adsorption on the printing frame plate.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram showing the main components of the embodiment, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1.

In FIG. 1, a printing frame 1 is made of a transparent glass plate or an acrylic resin plate. Since the printing frame 1 can be used for general purpose mask films of various sizes, it is preferable that the size of the printing frame 1 is large as long as the strength and surface smoothness can be maintained. A circuit pattern 1a+1b is printed on the printing frame 1 using a transparent conductive thin film.

Print formation of a transparent conductive thin film will be explained.

The transparent conductive thin film is made of a transparent conductive material.

Transparent conductive materials have the property of not absorbing but transmitting light in the vicinity of visible light, are good conductors of electricity, and are composed of semiconductors, typical examples of which include indium oxide and tin cadmium oxide. In this embodiment, an indium oxide thin film (hereinafter referred to as an ITO film) is used as the transparent conductive thin film.

Circuit pattern 1a and circuit pattern 1b are formed by ITO film.
The circuit patterns 1a and 1b are each formed in the shape of a comb tooth with a width of several millimeters and are combined with each other in a wedge shape, and the distance between the circuit patterns 1a and 1b is set to a uniform and constant dimension. The ITO film forming the circuit patterns la and lb has a thickness of several hundred to several μm.
It is an extremely thin coating, designed to have a thickness that does not affect the required light transmission.

Circuit pattern 1a and circuit pattern 1 formed with ITO film
A DC or AC voltage is applied by a power supply 2 between the voltages 1 and 2b, and the applied voltage is controlled by a regulator 3. In this embodiment, a variable resistor is used as the regulator 3.

A mask film 4 is attached to the printing frame 1 of FIG. 1 constructed as described above. FIG. 2 is a sectional view showing a state in which the mask film 4 is attracted to the printing frame 1. When the alignment with the workpiece is determined, a DC voltage is applied to the mask film 4 closely attached to the circuit patterns la and lb formed of the ITO film of the printing frame 1 by the power source 2. Due to the applied voltage, a negative charge is charged on the surface of the pattern 1a of the ITO film, and a positive charge is charged on the surface of the pattern 1b. Since the mask film 4 is made of polyethylene terephthalate, which is a high dielectric material, the surface of the mask film 4 is charged with the above-mentioned charges, and is attracted to the printing frame 1 by the attractive force between the charges.

Since the mask film 4 is lightweight and flexible,
It firmly adheres to the pattern surfaces 1a and lb of the printing frame 1. Since the glass plate and acrylic resin plate that make up the printing frame 1 are not processed with thin grooves for vacuum suction, the surface is smooth and the mask film 4 can be attracted to the suction surface even under normal pressure. No residual air or infiltration occurs.

The present invention is not limited to the above-described embodiments, but may take various forms when implemented.

For example, when forming circuit patterns la and lb using an ITO film, if variations occur in the transmission of light necessary for exposure and printing, it is necessary to
A structure may be adopted in which a transparent insulating film having the same light transmittance as the O film is formed to equalize light transmission through the printing frame. In this embodiment, the method of holding the mask film on the printing frame in the case of single-sided exposure has been described, but it goes without saying that the same method can be used in the case of double-sided exposure.

〔Effect of the invention〕

As explained above, according to the present invention, the mask film is held on the printing frame by electrostatic adsorption, so that the mask film firmly adheres to the circuit patterns of the transparent conductive thin film formed in large numbers several millimeters wide on the printing frame. Even when the main vacuum suction is performed to bring the workpiece and the mask film into close contact, the mask film is reliably held in the printing frame, which has the great effect of reducing exposure defects caused by misalignment of the mask film in the conventional method. If the size of the printing frame is designed appropriately, it can be used for mask films of many sizes, reducing the number of printing frames to be prepared, and reducing the size of the printing frame that was necessary with vacuum suction. No machining of intake grooves, etc. is required. Furthermore, since the attraction force of charge attraction can be easily adjusted by changing the applied voltage, the attraction force can be adjusted to suit various exposure conditions by simple operation of the variable resistor.

Due to the above effects, a method for holding a mask film is provided which is excellent in versatility and has a strong mask film holding power.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram of the main parts of a printing frame according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. It is a diagram of the main parts of the frame. The numbers in the figure indicate the following. 1...Printing frame 1a, lb...Transparent conductive thin film 2...Power supply 3...Adjuster 4.
...Mask film Fig. 1 Fig. 2 10 1t) 4

Claims (1)

[Claims] 1. A method for holding a mask film in an exposure apparatus, which comprises creating a circuit pattern using a transparent conductive thin film on a light-transmissible plate serving as a printing frame of the exposure apparatus, and applying a voltage to the mask film to cause the mask film to be charged and attracted.