JPH05333555A - Exposure method for printed circuit board - Google Patents

Abstract

PURPOSE:To provide the exposure method for printed circuit board which prevents position deviation from being generated and undercut from occuring at the time of development. CONSTITUTION:On the lower face of a rigid translucent board 3 of mask holder 2, the periphery of a mask film 1 is fixed in the completely air tight state by an adhesive tape 4, the mask holder 2 is dropped down in contact with a printed circuit board 7 mounted on an exposure stage 6 while adhering the mask film 1 to the translucent board 3 of the mask holder 2 by sucking air from the mask holder side, a space 11 between the mask holder 2 and the exposure stage 6 is sucked, suction on the mask holder side is stopped and after the space between the mask film 1 and the translucent board 3 of the mask holder 2 is opened to atmosphere, exposure is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exposing a printed circuit board.

[0002]

2. Description of the Related Art In a printed circuit board manufacturing process, after a circuit pattern is formed on a printed circuit board by a copper foil,
Solder resist ink is applied on the entire surface, and in order to remove the solder resist layer on the land,
A mask film is placed and exposed to light for development, and the solder resist ink on the portion that has not been polymerized and cured because it is not exposed is washed away. The printed circuit board automatic exposure device for solder resist is a device for exposing by exposing a mask film on a printed circuit board coated with solder resist ink.

There are various types of automatic exposure apparatus for printed circuit boards for solder resist, but as shown in FIG. 4, for example, an exposure stage 21 and a mask holder 22 are provided, and the exposure stage 21 is planarized by a positioning device 23. The angle is changed by moving in the X-axis and Y-axis directions at the top. A CCD camera 24 for alignment and an exposure ultraviolet lamp 25 are arranged above the mask holder 22. As shown in FIG. 5, the mask film 26 is fixed to the lower surface of the translucent plate 22c of the mask holder 22 with an adhesive tape 26a at required points, and the hole 22a is further formed.
Vacuumed from. A rubber pad 22b is provided around the lower surface of the mask holder 22.

A printed circuit board 27 on which a circuit pattern is formed of copper foil and a solder resist ink is applied on the entire surface to form a solder resist layer 27a.
Is sent to the solder resist printed circuit board automatic exposure device by the carry-in conveyor 28, adsorbed by the carry-in handler 29, and placed on the exposure stage 21. The mask holder 22 to which the mask film 26 is closely attached descends halfway, and while the CCD camera 24 detects the positioning mark, the positioning device 23 moves to position the printed board 27 with respect to the mask film 26.

Next, as shown in FIG. 6, the mask holder 22 is further lowered, and the mask film 26 is placed on the printed circuit board 27.
, The rubber pad 22b is brought into close contact with the exposure stage 21, vacuum suction is performed from the hole 21a of the exposure stage 21 to create a vacuum between the mask film 26 and the exposure stage 21, and the mask film 26 is placed on the printed circuit board 27.
UV lamp 25 for exposure in this state.
Exposure is performed. Printed circuit board 2 after exposure
7 is adsorbed by the carry-out handler 30, placed on the carry-out conveyor 31, and sent to the next developing step.

[0006]

However, since the surface of the printed board 27 has irregularities in the portion where the copper foil of the circuit pattern is formed and the portion where the copper foil is not formed, the solder resist layer applied thereon is formed. The surface of 27a is also uneven. Therefore, even if the mask holder 22 descends, the mask film 26 comes into contact with the surface of the solder resist layer 27a, and vacuum suction is performed from the exposure stage 21 side to create a vacuum between the mask film 26 and the exposure stage 21. The mask film 26 does not completely adhere to the printed circuit board due to the unevenness on the surface of the printed circuit board.

Therefore, the peripheral edge (edge) 2 of the portion where the solder resist layer is to be removed, which surrounds the land portion 27b where the solder resist layer is to be removed when exposed to light.
7c is defocused, the solder resist layer on the peripheral edge 27c is not vertically divided and is not removed when developed, and is removed obliquely as it approaches the printed circuit board surface 27 in the thickness direction of the solder resist layer as shown in FIG. The so-called undercut occurs.

Therefore, it is necessary to widen the space between the adjacent land portions. However, circuit patterns on printed circuit boards are becoming finer, and there is an increasing demand for narrower intervals between lands.

If the light transmitting plate is made of a soft material in order to improve the close contact between the mask film and the printed circuit board, a displacement occurs when the transparent plate is brought into close contact with the printed circuit board.

It is an object of the present invention to provide a method of exposing a printed circuit board which does not cause a positional deviation and does not cause an undercut when developed.

[0011]

According to the method of exposing a printed circuit board of the present invention, a mask film is fixed to the lower surface of a rigid light-transmitting plate of a mask holder with an adhesive tape so that the periphery thereof is completely airtight. While vacuum suctioning the mask film to the transparent plate of the mask holder, lower the mask holder until it touches the printed circuit board placed on the exposure stage, and vacuum the space between the mask holder and the exposure stage. While sucking, the vacuum suction on the mask holder side was stopped, the space between the mask film and the light-transmitting plate of the mask holder was opened to the atmosphere, and then exposure was performed.

[0012]

By opening the space between the mask film and the light-transmitting plate of the mask holder to the atmosphere, the mask film completely adheres along the irregularities on the surface of the printed circuit board, and the solder resist layer should be removed. Edge of part
Is not blurred, and undercut does not occur when developed.

[0013]

1 to 3 are views for explaining the method of the present invention, in which a mask film 1 is covered with an adhesive tape 4 on the lower surface of a rigid transparent plate 3 of a mask holder 2, and the entire circumference thereof is completely covered. Secure to airtight. Then, vacuum suction is performed from the suction hole 5 on the mask holder side to bring the mask film 1 into close contact with the lower surface of the transparent plate 3 of the mask holder. On the other hand, the exposure stage 6
A circuit pattern 8 is formed of copper foil on the printed circuit board 7 placed thereon, and a solder resist layer 9 is formed thereon.

In this state, after the mask holder 2 is aligned, it is lowered until it comes into contact with the printed circuit board 7 mounted on the exposure stage 6. The rubber pad 10 provided on the mask holder 2 contacts the upper surface of the exposure stage 6,
A closed space 11 is formed between the mask holder 2 and the exposure stage 6. The space 11 is vacuum-sucked from the suction hole 12 on the exposure stage 6 side. Next, the vacuum suction on the mask holder 2 side is stopped, and the suction hole 5 is opened to the atmosphere.

Then, the mask film 1 adheres to the surface of the solder resist layer 9 along the irregularities. After that, exposure is performed and vacuum suction is released from the suction hole 12 on the exposure stage 6 side, and the mask holder 2 is raised.

[0016]

In the method of the present invention, the space between the mask film and the light-transmitting plate of the mask holder is opened to the atmosphere prior to the exposure, so that the mask film follows the unevenness of the surface of the printed circuit board. Fully adhered, the edge of the part where the solder resist layer should be removed is not blurred,
Undercut does not occur when developed.

Further, since the mask film is held by the rigid light-transmitting plate of the mask holder and the periphery thereof is completely fixed by the adhesive tape, the mask film is not displaced even when it is brought into close contact with the printed circuit board.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of exposing a printed circuit board according to the present invention.

FIG. 2 is a view showing a state where a mask holder is lowered.

FIG. 3 is a diagram showing a state in which a space between a mask film and a transparent plate of a mask holder is open to the atmosphere.

FIG. 4 is a diagram showing the entire solder resist printed circuit board automatic exposure apparatus.

FIG. 5 is an enlarged view of a mask film and a mask holder portion in a conventional method.

FIG. 6 is a view showing a state where a mask holder is lowered by a conventional method.

FIG. 7 is a view showing a state in which an undercut is made.

[Explanation of symbols]

 1 Mask Film 2 Mask Holder 3 Light-transmitting Plate 4 Adhesive Tape 5 Suction Hole 6 Exposure Stage 7 Printed Circuit Board 8 Circuit Pattern 9 Solder Resist Layer 10 Rubber Pad 11 Space 12 Suction Hole

Claims (1)

[Claims] 1. A mask film is fixed on a lower surface of a rigid light-transmitting plate of a mask holder with an adhesive tape so that the periphery thereof is completely airtight, and vacuum suction is applied from the mask holder side to remove the mask film from the light-transmitting plate of the mask holder. While adhering to the mask holder, lower the mask holder until it touches the printed circuit board placed on the exposure stage, vacuum suction the space between the mask holder and the exposure stage, and stop the vacuum suction on the mask holder side. A method for exposing a printed circuit board, which comprises exposing a space between a film and a light-transmitting plate of a mask holder to the atmosphere and then exposing.