JPS63138347A - Formation of photosolder-resist coating - Google Patents

Abstract

PURPOSE:To enable alignment of a printed wiring board and an exposure mask before photocuring a photosolder-resist layer by forming an image capable of confirming the position of the exposure mask with vision by irradiating light on a layer composed of a high polymer for the alignment. CONSTITUTION:A liquid photosolder-resist material (a) is applied on the substrate (c) of the printed wiring board followed by applying a solution (b) of the high polymer which has transparency for an active ray and contains a dye capable of effecting photolysis at a specific wavelength range on the obtd. substrate. The obtd. substrate irradiate the light (e) through the exposure mask (f), thereby effecting the photolysis of the dye and the alignment exposure, and the active light (g) is irradiated to the photosolder-resist (a) to effect the photocuring exposure. And, the photosolder-resist material (a) is developed, followed by removing the cured part of the photosolder-resist material. The high polymer coating (b) irradiates the light having the specific wavelength range in the amount necessary for effecting the photolysis of the dye, thereby confirming the position of the exposure mask with vision by referring to the discoloring and the undiscoloring parts of the dye, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a foot solder resist film for a printed wiring board.

(Prior Art) Conventionally, solder resist coatings for printed wiring boards have been manufactured by applying printed solder resist ink onto printed wiring boards using a screen printing method. Because of problems such as bleeding and bleed phenomenon after printing, it has been difficult to achieve high precision.

In order to solve these problems, a film-like photo solder resist that has high resolution and can support high precision has been commercially available. However, such film-like photo solder resists do not have sufficient heat resistance, and in addition, bubbles tend to form during thermocompression bonding using a vacuum laminator, and it is difficult to fit the edges between dense patterns. , blistering of the solder resist film and poor adhesion are likely to occur, and it has become impossible to cope with the recent increase in the density of printed wiring boards.

For this reason, as shown in JP-A No. 61-272, a liquid photo solder resist based on epoxy resin with excellent adhesion, heat resistance, solvent resistance, and insulation properties was developed to improve heat resistance. It has come to pass. However, in order to use such a liquid photo solder resist to form a solder resist film that is compatible with higher precision and higher density printed wiring boards, there is no need to consider the expansion and contraction of the exposure mask during exposure work. , a binning exposure using a glass dry plate is required. However, when performing exposure using a glass dry plate, the positional misalignment between the printed wiring board and the exposure mask cannot be clearly confirmed during exposure because the photosensitive emulsion of the glass dry plate is a living body of silver salt. Is it convenient for manufacturing to be able to visually check the positional relationship with the board immediately after exposure?Currently, right after exposure, you can visually check the parts of the solder resist that are exposed to light and the parts of the solder resist that are not exposed to light. There is no known liquid photo solder resist that can be produced, and therefore, there is a problem in that it is not possible to confirm displacement of the solder resist film due to misalignment between the printed wiring board and the exposure mask until after development has been completed.

(Problems to be Solved by the Invention) As described above, solder resists for printed wiring boards have changed from printed solder resist inks to film-like photo solder resists, in response to demands for higher precision and higher density.
Furthermore, improvements such as liquid photo solder resist as a material for forming solder resist coatings for high-density printed wiring boards have been progressing rapidly, but the exposure work that accompanies changes in materials has been made. This is not accompanied by the simplification of . That is, as mentioned above, 1
For example, when exposing liquid photo solder resist, do you have to use an exposure mask that uses a glass dry plate that is aligned with pins (glass dry plate exposure)? This is because there are no changes that can be judged by the operator's eyes.

It is not possible to know whether the photo solder resist has been exposed at the correct position and reliably until it is developed. For this reason, in the assembly work, it was necessary to run the preceding amount until development in order to confirm the misalignment between the printed wiring board and the exposure mask. Furthermore, after the development bond is completed, if the positional deviation between the printed wiring board and the exposure mask is confirmed, it is necessary to perform a reprocessing process in which the photo solder resist material is peeled off and the photo solder resist material is applied again. Ta. Furthermore, immediately after exposure, exposed items cannot be distinguished from unexposed items, resulting in problems such as unexposed items and double exposure. In other words, even if materials for photo solder resist coatings that can cope with higher density printed wiring boards have been developed, no method has been proposed to make them easier to use in actual manufacturing operations.

Therefore, the inventors have conducted intensive research on a method for efficiently using materials for improved photo solder resist coatings, and have found that the materials can be coated on top of the materials by non-photocuring light. The present invention was completed based on the new finding that the position of the exposure mask can be clarified by forming a film containing a dye that causes a color tone change and once exposing this film to light.

The present invention was made in view of the above-mentioned conventional problems, and its purpose is to enable use with high precision and high density, and to solve the problem of misalignment or alignment between a printed wiring board and an exposure mask. Exposure work for! It is an object of the present invention to provide a method for forming a liquid photosolder resist film that can be visually confirmed afterwards and can be confirmed before photocuring exposure.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the means taken by the present invention is to provide a photosensitive resin having an acrylic group or a metagril group as a photosensitive group and an epoxy group as a thermosetting group. A liquid photo solder resist material that includes a process of applying a liquid photo solder resist material containing a hardening agent to a printed wiring board and then returning it, and a dye that photodecomposes in a specific wavelength range. A step of applying a solution made of a polymer that is transparent to actinic rays onto the photo solder resist material and then drying it to form a film made of the polymer, and applying it through an exposure mask. A step of irradiating a film made of ItI polymer with light to photodecompose the dye and performing alignment exposure, and irradiating the photo solder resist material with actinic rays through the exposure mask. a step of performing photocuring exposure to light, a step of removing the uncured portion of the photo solder resist material by removing the film made of the high molecular weight polymer, and a step of removing the photo solder resist material of the photo cured portion. This is a method for forming a photo solder resist film, which comprises the step of further thermally curing the photo solder resist film.

Here, the acrylic group or methacrylic group imparts photocurability to the liquid photosolder resist material, and the epoxy group imparts thermosetting properties to the liquid photosolder resist material, and also imparts photocurability to the liquid photosolder resist material. It imparts heat resistance to the resist film. The curing agent is used to speed up the thermal curing speed of the photo solder resist material, and to impart adhesion, solvent resistance, and insulation properties.

Examples of curing agents include boron trifluoride alkylamine complexes, imidazoles such as 2-ethyl-4-methylimidazole, and 4-curing agents such as trimethylbenzylammonium chloride.
Examples include polyamines such as amine salts, dicyandiamide, and isophorone diamine, and imidazoles are preferred from the viewpoint of storage stability.

In addition to the hardening agent described above, pigments, fillers, flame retardants, antifoaming agents, and solvents can also be added to this liquid photo solder resist material.

The method for applying liquid photo solder resist material is as follows:
Examples include curtain coating method, screen printing method, and roll coating method.

The dye should preferably be one that can be used under normal yellow light;
A material that photodecomposes and fades in the wavelength range of ~400 nrn is preferable, and crystal violet, methylene blue, or rhodamine B can be used as such materials.

As the polymer, water-soluble polymers such as polyvinyl alcohol and gelatin are preferable.The reason why water-soluble polymers are preferable is that when alignment exposure is performed, if misalignment is found, , only the coating made of this high molecular weight polymer was washed with water or hot water to make the cylinder 21cm thick.
This is because the film can be easily re-formed by reapplying a new water-soluble polymer.

More preferably, a decomposition accelerator is added to the solution made of this high molecular weight polymer, because this decomposition accelerator is effective in decomposing the dye with a small amount of light. Examples of this decomposition accelerator include benzophenones such as benzophenone and Michler's ketone, 2-
Examples include anthraquinones such as ethyl anthraquinone, acyloins such as benzoin and its alkyl ether derivatives, and effects are usually obtained in the range of 0.1-10%. The amount of dye added is 0 to the high molecular weight polymer.
．． 1S is preferably 10%, more preferably 1 to 3%.

Examples of methods for applying a solution made of a high molecular weight polymer include a dip coating method, a curtain coating method, and a roll coating method, and the dip coating method is preferable from the viewpoint of workability.

According to the invention, in a glass plate exposure operation.

First, the polymer coating is irradiated with light in a specific wavelength range necessary for photodecomposing the dye, so that only the polymer coating is exposed.

As a result, an image corresponding to the exposure mask appears on the polymer film, and the positional deviation between the printed wiring board and the exposure mask is confirmed by referring to this image. In other words, by irradiating the polymer coating with light at a specific wavelength that is sufficient for the dye to photodecompose, the dye in the light irradiated area will fade, and the color of the dye in the light beam irradiated area will change. I don't. Therefore, by referring to the faded and unfaded areas of the dye, it is possible to visually confirm the position. Therefore, there is no need to run the previous product through development to check for misalignment between the printed wiring board and exposure mask, and there is no need to recycle the previous product where misalignment between the printed wiring board and exposure mask has been confirmed. . Furthermore,
This also eliminates the occurrence of unexposed items and double exposure.

Furthermore, polyvinyl alcohol and gelatin as the polymers used in the present invention are inexpensive, and the amount of dyes and photodegradation accelerators used is small, so it is costly to reapply the polymers. is not significantly affected.

In addition, since no dye is mixed into the liquid photo solder resist material, the storage stability of the epoxy group, which is a thermosetting group, is good. The color of the pigment and the color of the dye in the solder resist material do not mix, and the change in color after exposure can be clearly recognized.

(Actions of the Invention) By employing the child actors as described above, the present invention has the following effects.

In the method for forming a photo solder resist film according to the present invention, the dye in the light irradiated area is The color fades, and the dye in the light beam irradiation area does not change color.

Therefore, by referring to the faded and unfaded areas of the dye, it is possible to visually confirm the position.

Next, check the positional misalignment between the printed wiring board and the exposure mask, and find out that it is only 2gl! After performing this, necessary portions of the photosolder resist material are photocured by irradiating actinic rays for photocuring the photosolder resist material. In this case, the photosolder resist material and the dye are not mixed and are separated into layers, so that no reaction occurs between the epoxy groups in the photosolder resist material and the dye.

Next, the present invention will be described in detail with reference to examples.

(Example) The composition of the liquid photosolder resist material used in each of the following examples is shown below.

Acrylic modified epoxy resin 30g Poly(styrene/methacrylic acid/β-hydroxyethyl methacrylate) 50g P-methoxyphenol 0.1g Benzoin methyl ether 3g 2-ethyl-4
-Methylimidazole 15g Methyl ethyl ketone
2001 sentence phthalocyanine green
0.5g silicone oil 0
．． 75g Example 1 The liquid photo solder resist material was applied to a printed wiring board by a curtain coating method, air-dried for 15 minutes, and then dried to the touch at 80° C. for 20 minutes. (See Figure 1) Next, a solution consisting of a high molecular weight polymer having the following composition was applied to this printed wiring board using a dip coating method, air-dried for 15 minutes, and then dried at 40°C for 30 minutes. A film made of this high molecular weight polymer was formed on top of the photo solder resist material. (See Figure 2) Polyvinyl alcohol (average degree of polymerization 1500, degree of saponification 86.5-89.0 sof
fi$) Part 5 Crystal Violet
0.02 parts water
9581 Next, using a glass dry plate, the polymer film thus formed was first irradiated with light in the wavelength range of 350 to 400 nm (see Figure 3) to form a printed wiring board. We checked for any misalignment with the exposure mask. Since there was no problem with the zero misalignment, we left the glass dry plate in the same position and used a high-pressure mercury lamp to apply an activity of 500 sJ/am'' to the photo solder resist material. The photo solder resist material was photocured by irradiating it with light (see Figure 4).

The polymer film was immersed in a hot water bath at 50° C. for 1 minute to dissolve and peel off (see FIG. 5), drained and dried, and then developed to remove unnecessary portions of the photo solder resist material.

Finally, by heat curing at 150°C for 1 hour, the 6th
A photo solder resist film as shown in the figure was formed.

Example 2 The liquid photo solder resist material was applied to a printed wiring board by a curtain coating method, air-dried for 15 minutes, and then dried to the touch at 80° C. for 20 minutes.

A solution consisting of a high molecular weight polymer having the following composition was applied on top of this using the dip coating method, and after air-drying for 15 minutes,
It was dried at 0° C. for 3 a >,) to form a film of about 1 to 2 gm of high molecular weight polymer on the photo solder resist material.

Polyvinyl alcohol (average degree of polymerization 1500, degree of saponification 86.5-89.0■0%) 5 parts Methylene blue 0.02 parts Benzophenone 0.02 parts Water
95 parts The following steps were carried out in the same manner as in Example 1.

Apply the liquid photo solder resist material to the printed wiring board using the curtain coating method! ! After drying in the air for 15 minutes, drying to the touch was performed at 80° C. for 20 minutes.

From this step, a solution consisting of a high molecular weight polymer having the following composition was applied using the dip coating method, and after air drying for 15 minutes,
It was dried at 48° C. for 30 minutes to form a film made of a high molecular weight polymer on the photo solder resist material.

Polyvinyl alcohol (average degree of polymerization 1500, degree of saponification 86.5-89.0 soJ1%) 5 parts Crystal violet 0.0.411 Benzophenone 0.01 part Michler's ketone 0.01 part Water
As the exposure mask in the example of 95 copies or more, a glass dry plate on which the desired circuit is formed is used, and the wavelength range from 350 to
When 4Q Onm light was irradiated to check for any misalignment between the printed wiring board and the exposure mask, it was visually confirmed that some misalignment had occurred.

In order to correct this misalignment, the W1 adjustment was made to the position of the glass dry plate, and the printed wiring board used to confirm the misalignment between the printed wiring line and the exposure mask was placed in a hot water bath at 50°C for 1 minute. The wood was immersed, and only the coating made of the high molecular weight polymer was dissolved and peeled off, and then the wood was cut and dried. Thereafter, a solution consisting of a polymer having each of the above compositions was applied onto the photo solder resist material by dip coating, air-dried for 15 minutes, and then dried at 40°C for 30 minutes to form the photo solder resist material. A film made of a high molecular weight polymer was again formed on the resist material.

After doing the above, I performed a light exposure again to confirm the misalignment between the printed wiring board and the exposure mask, and there was no problem, so I irradiated the photo solder resist with active light. The material was photocured.

Next, this printed wiring board was immersed in a hot water bath at 50°C for 1 minute to dissolve and peel off the coating made of high molecular weight polymer, and after draining and drying, development was performed to remove the photo solder resist material. Finally, a photo solder resist film was formed by heat curing at 150° C. for 1 hour.

Example 4 The liquid photo solder resist material was applied onto one side of a printed wiring board using a curtain coater, air-dried for 15 minutes, and then dried to the touch at 80°C for 20 minutes. Apply using the above method and air dry.

Dry to the touch.

The following combination of solutions was used as a solution consisting of a high molecular weight polymer.

Gelatin 5 parts Crystal Violet 0.02 parts Bencibuenone
0.02 parts water
95 parts The other steps were carried out in the same manner as in Example 1.

In all of the above examples, only the dye in the coating made of high molecular weight polymer was partially bleached before photocuring the photo solder resist material, so that the position of the printed wiring board and the exposure mask was Even if it is out of alignment,
This can be easily confirmed visually, so that's it! ! I
Adjustments could be made easily.

(Effects of the Invention) As detailed above, in the present invention, as shown in the above embodiment, it is possible to handle high density, and the positional deviation between the printed wiring board and the exposure mask is aligned and immediately after the exposure operation. This makes it possible to provide a method for forming a photo solder resist film that can be visually recognized and finely adjusted by one position shift on the spot.

That is, in the method for forming a photosolder resist film according to the present invention, a layer made of a high molecular weight polymer containing a dye is formed on a photosolder resist layer, and at the same time, before the photo-solder resist layer is photocured. The layer made of high molecular weight polymer is irradiated with light for positioning, so that an image that can be visually confirmed at the position of the exposure mask is formed on the layer made of high molecular weight polymer. , the printed wiring board and the exposure mask can be aligned before photocuring the photo solder resist layer.

In addition, since the layer made of high molecular weight polymer is formed as a water-soluble material, even if the printed wiring board and the exposure mask are misaligned, the layer made of high molecular weight polymer can be easily removed. It is possible to create this type of printed wiring board without waste! It is possible to do this.

[Brief explanation of the drawing]

Each of FIGS. 1 to 6 UA is a partially enlarged cross-sectional view illustrating the method of forming a photo solder resist film of the present invention in order, and FIG. A cross-sectional view of the coated state; Figure 2 is a cross-sectional view of the state in which a film made of a polymer is formed on the photo solder resist material; Figure 3 is a cross-sectional view of the state in which a film made of a polymer is formed on the photo solder resist material; FIG. 4 is a cross-sectional view of the photo solder resist material being exposed to light; FIG. 5 is a cross-sectional view of the photo solder resist material with the coating removed. FIG. 6 is a cross-sectional view of the photo solder resist material after it has been thermally cured. Explanation of symbols a... Photo solder resist material, b... Coating made of high molecular polymer, c- Base material (of printed wiring board), d
...Conductor circuit, e...Light, f...Exposure mask-1
g...Active rays. that's all

Claims (1)

[Scope of Claims] 1) A method for forming a photo solder resist film, characterized by sequentially performing the following first to sixth steps. (a) Acrylic group or methacrylic group as a photosensitive group,
A first step of applying a liquid photosolder resist material containing a curing agent, which has an epoxy group as a thermosetting group, onto a base material of a printed wiring board and then drying it. (b) Contains a dye that photodecomposes in a specific wavelength range,
A solution made of a high molecular weight polymer that is transparent to actinic rays,
A second step of coating the photo solder resist material and drying it to form a film made of a high molecular weight polymer. (c) A third step of irradiating the film made of the high molecular weight polymer with light through an exposure mask to photodecompose the dye and performing positioning exposure. (d) A fourth step of irradiating the photo solder resist material with actinic rays through the exposure mask to perform photocuring exposure. (E) A fifth step of developing the photo solder resist material after peeling off the film made of the high molecular weight polymer, and removing the uncured portion of the photo solder resist material. (F) A sixth step of further heat-curing the photo-cured portion of the photo-solder resist material.