JPH0567861A - Coating method of photoresist - Google Patents

Abstract

PURPOSE:To provide the coating method of photoresist in even thickness over the whole surface of a printed wiring in order to manufacture a printed-wiring circuit board. CONSTITUTION:Within the coating method of photoresist using the dip process of boards, exceeding one cycle comprising the immersion, picking-up, drying-up and 180 deg. turning step on the axis in the normal direction to the immersion direction is to be repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a photoresist film on a printed wiring substrate when manufacturing a printed wiring circuit board.

[0002]

2. Description of the Related Art In recent years, a printed wiring board is manufactured by coating a base material of a copper polyimide resin substrate with a photoresist,
Reverse pattern exposure development, then copper additive plating, photoresist stripping, sputtered copper flash etch, then photoresist coated on both sides, polyimide film both sides exposed and developed, polyimide film After chemical etching is performed to make holes, the photoresist is peeled off, and then finish-finished to manufacture a printed wiring circuit board. In the production of these printed circuit boards, it is necessary to apply photoresist to the copper polyimide resin board in the first step. With a dip coater,
The dip coating method of applying photoresist is a dipping fixing jig, in which a copper-polyimide resin substrate is attached to a thin metal plate (stainless steel plate, copper plate), fixed vertically, and submerged in a tank filled with photoresist at a constant speed, and immersed for a few seconds. After that, it is carried out by a method of pulling up again at a constant speed. When the coating is carried out at a constant speed by this method, the photoresist hangs due to gravity, resulting in uneven film thickness in the upper 1/3 to 1/4 portion. If there is a variation in the film thickness within one sheet, the adhesion to the mask will deteriorate and the edges of the photoresist pattern after development will become dull. If the edge of the photoresist pattern is not perpendicular, the circuit cannot be formed accurately in the plating forming process. Therefore, it is desirable that the photoresist has a film thickness of at least ± 2 μm with respect to the center value over the entire surface of the copper sputtered polyimide substrate. However, in the dip coating method, the thickness of the photoresist film is large and the thickness thereof is large. Often exceeds 5 μm, and a copper-polyimide resin substrate having an actually effective photoresist film thickness is hardly obtained.

As a solution, as a method for obtaining a uniform film,
A method of shifting the pulling speed in three steps has been proposed, but even if the pulling speed is changed, it is not possible to completely eliminate the unevenness of the photoresist film thickness on the upper and lower parts, and a uniform film cannot be obtained. Is occurring.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a method of coating a photoresist film having a uniform thickness on the entire surface of a printed wiring board.

[0005]

[Means and Actions for Solving the Problems] That is, in the method for applying a photoresist according to the present invention, a printed wiring board is mounted on a dip-fixing jig of a dip coater, fixed vertically, and placed in a tank filled with the photoresist. Immersion at a constant speed, and then a few seconds later, it is pulled up again at a constant speed In the method of coating a photoresist by the dip method, the coated substrate is immersed, then pulled up, dried, and then rotated in the direction normal to the immersion direction. It is characterized in that one cycle consists of rotating 180 ° as the axis of rotation, dipping, and then pulling up and drying, and this cycle is performed once or more.

FIG. 1 is a diagram showing the relationship between the viscosity of the photoresist and the film thickness of the photoresist when the photoresist is applied in one cycle. Actually, the viscosity of the photoresist may be adjusted according to the desired photoresist film thickness. When the cycle in this experiment is one cycle, it is possible to apply the photoresist film thickness uniformly over the entire surface. The accuracy at that time can be controlled to ± 2 μm. When it is desired to apply the photoresist more accurately, the viscosity of the photoresist can be lowered and the cycle can be performed twice or more to obtain the desired photoresist film thickness. As described above, it is advantageous to increase the cycle in terms of obtaining a uniform film thickness, but since the number of drying steps increases, it may be determined in consideration of work efficiency and the like.

[0007]

[Example] Copper sputtered polyimide film substrate (trade name: ETCH-A-FLEX Southwall Co., Ltd.) on one side of a rectangular stainless steel plate having a thickness of 1 mm and a length and width of 360 mm x 260 mm, thickness of 50 μm, length and width of 340 mm x 240 mm Was laminated with the copper surface facing outward, and laminated with a masking tape to prevent air from entering. Next, the three points on one side of the outer circumference of the stainless steel plate to which the copper-polyimide film substrate was attached were fixed with clips and hung, and the room temperature was set to 25.
The test was carried out in an environment of ℃ and humidity of 55% or less. Kinematic viscosity is 40c
ps negative resist made by Tokyo Ohka Kogyo [Product name PME
RNHC-600] was immersed in a tank filled with 5 mm of the upper portion, and after the liquid surface was sufficiently stationary, it was pulled up after 5 seconds. The dip coating conditions at this time are shown below.

After pulling up at a constant pulling speed of -30 mm / sec, it was hung in a dryer and air-dried for 5 minutes, then hung with a clip for 15 minutes at 70 ° C., dried with hot air, cooled, and the resist dipping direction was measured. It is rotated 180 ° about the line direction, pulled up again at a pulling speed of -30 mm / sec, hung in a dryer for 5 minutes, and then dried at 70 ° C.
Hot air drying for 30 minutes. In this way, the copper polyimide film substrate obtained by dipping into the dip coater tank an even number of times was cooled, and then a portion of 3 cm from the outer periphery was cut over the entire periphery to obtain one copper polyimide substrate having one side coated with a resist. Table 1 shows the results of measuring the thickness of the photoresist film thickness on the copper polyimide substrate obtained by this method.

[0009]

[Table 1]

From the results shown in Table 1, it can be seen that the photoresist coating method of the present invention can provide a photoresist thick film having a small variation in thickness.

As a comparative example, the pulling speed is 30 mm / se.
After pulling it at a constant speed of c, it was air dried by hanging it in a dryer for 5 minutes, then it was air dried at 70 ° C for 15 minutes, then cooled, and the resist dipping direction was rotated 180 ° about the normal direction axis and the pulling speed was again. After pulling at a speed of 30 mm / sec, air-drying for 5 minutes, then hot air drying at 70 ° C. for 30 minutes, pulling up again at a constant speed of 30 mm / sec, and then air-drying in a dip coater for 5 minutes. 30 at 70 ° C
Hot air drying was performed for a minute. Table 2 shows the results of measuring the thickness of the photoresist film thickness on the polyimide substrate in the case of the method of dipping in the tank tank of the dip coater three times (dip odd number of times) in this way.

[0012]

[Table 2]

From the results in Table 2, it can be seen that in this example, the photoresist film thickness greatly increases as it goes downward. The photoresist film thickness is MItutoyo.
The measurement was performed using a contact dial gauge manufactured by the company.

[0014]

According to the photoresist coating method of the present invention, regardless of whether it is a thin film or a thick film, it is possible to obtain a copper polyimide substrate, a thin metal film, etc., on the entire surface of which a photoresist film having a uniform variation is coated. According to the present invention, it becomes possible to manufacture a high-density, high-performance multilayer printed wiring board.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the viscosity of a liquid photoresist used in an example of the present invention and the film thickness of a resist.

Claims (1)

[Claims] 1. A dipping method in which a printed wiring board is mounted on a dip-fixing jig of a dip coater, fixed vertically, immersed in a tank filled with photoresist at a constant speed, and several seconds later, pulled up at a constant speed again. In the method of applying a photoresist according to 1., the coated substrate is soaked, then pulled up and dried, and then rotated by 180 ° with the normal direction to the dipping direction as the axis of rotation, soaked, and then pulled up and dried. A method of applying a photoresist, characterized in that one cycle is performed once or more.