JP7419905B2 - Resin film remover for circuit boards - Google Patents

Description

The present invention relates to a resin film remover for circuit boards, and more particularly, it is used to remove removable resin materials coated on the main surface of a board during the manufacture of electronic circuit boards under mild conditions. The present invention relates to an aqueous stripping agent.

In recent years, in the field of electronic information equipment, improvements in the precision of electronic circuit members have been pursued year by year. When manufacturing these highly precise parts, curable resin materials that can respond to external stimuli such as heat and light are essential.
For example, as a method for forming functional elements such as three primary color pixels of electronic circuits and color filters, a curable resin is applied onto a substrate, and the formation area of the functional element is divided depending on whether or not it is covered with a cured resin film. Form a functional element.
In addition, with the trend toward smaller and lighter electronic devices, it is not only essential to manufacture them in a cleaner environment, but also the presence of minute foreign objects and shocks generated during processing operations can damage the surface of the substrate. Since there is a high possibility of damage, there are increasing cases where a curable resin is coated on the surface of the substrate and cured to form a temporary resin film aimed at reducing the defect rate.
These curable resins require a removal process after use, and a common method for removing them is chemical removal using an alkaline chemical.

Patent Document 1 discloses a resist stripping agent that can be removed using a strong alkaline aqueous solution containing quaternary ammonium hydroxide as the stripping agent.
While the stripping agent of Patent Document 1 can reduce the effect on the substrate surface, it requires the equipment piping for the stripping process to be made of a material that is resistant to solvents and alkalis, and because it contains quaternary ammonium hydroxide, There are concerns about issues such as high environmental impact and waste liquid treatment costs.

Further, Patent Document 2 discloses a protective film composition for dicing that can be removed using an amine aqueous solution such as an ammonia aqueous solution or a tetramethylammonium hydroxide aqueous solution as a stripping agent.
Although the protective film of Patent Document 2 has good peeling performance in a pH range of 11 or higher, the solubility of the peeling agent is insufficient and residual pieces of the resin film remain on the circuit board after the peeling process. In some cases, the resin film peeled off from the circuit board did not dissolve.

Japanese Patent Application Publication No. 2015-118124 Japanese Patent Application Publication No. 2018-129365

Under these circumstances, there are currently no restrictions from the perspective of avoiding adverse effects on users and the environment in which they are used, and there are currently no restrictions on the use of resin films formed using curable resins on the substrate surface in the manufacturing process of electronic circuit boards. There is a need for a stripping agent that can be more easily removed from the surface.
An object of the present invention is to provide a stripping agent for removing a resin film formed using a curable resin on the surface of an electronic circuit board, and to easily remove the resin film from the electronic circuit board, which is a workpiece, in a short time. It is an object of the present invention to provide a stripping agent that can be removed quickly, leaves less residual pieces of the resin film on a circuit board, and has less adverse effects on users and the environment in which it is used.

In order to achieve the above object, the present inventors conducted extensive studies and found that the above problem could be solved by combining specific components shown below.
That is, the present invention provides a salt of an aromatic acid selected from the group consisting of an aromatic carboxylic acid having 7 to 9 carbon atoms and an aromatic sulfonic acid having 6 to 8 carbon atoms, and an alkanolamine having 2 to 10 carbon atoms. This is a resin film removing agent for circuit boards containing:
The present invention also provides a step of forming a resin film on the main surface of a circuit board using a removable curable resin, and removing the resin film by bringing the resin film stripping agent for circuit boards into contact with the resin film. A method of manufacturing an electronic circuit board is also provided, including the step of removing.

Since the release agent of the present invention has high peeling performance, the resin film formed on the electronic circuit board to be processed can be brought into contact with the resin film by dipping, spraying, etc. for a short period of time. It can be easily removed with a , and there are few residual pieces of the resin film on the circuit board.
Further, since the stripping agent of the present invention has a liquid property in the neutral to slightly alkaline range, it has little impact on the user and the environment in which it is used.
Furthermore, each component constituting the stripping agent of the present invention can be easily produced by industrial methods such as synthesis, which is advantageous in terms of production cost.

Embodiments of the present invention will be described below.
The resin film stripping agent for circuit boards of the present invention (hereinafter sometimes referred to as "the stripping agent of the present invention") contains a salt of the following aromatic acid and the following alkanolamine as an active ingredient.

[Aromatic acid]
The aromatic acid used in the present invention has an aromatic ring in its molecular structure, and is an Arrhenius acid, that is, a monobasic acid, which generates one proton per acid group in the solvent system on the aromatic ring. It is a compound that has an acid group belonging to the group. In the present invention, one kind of a plurality of aromatic acids can be used alone or two or more kinds can be used in combination.

From the viewpoint of the removability and water solubility of the resin film, the number of aromatic rings that the aromatic acid has is preferably 2 or less.
The acid group, ie, the functional group exhibiting acidity, is preferably a carboxylic acid group or a sulfonic acid group. Aromatic acids can be polyvalent acids depending on the number of functional groups, but monovalent or divalent aromatic acids are preferred in the present invention, and the acid dissociation constant (pKa) of the aromatic acid in an aqueous solution is determined by the peeling effect. From this point of view, a value of 4.0 or less is preferable.
From the viewpoint of the peeling effect of the resin film, the total carbon number of the aromatic carboxylic acid is preferably 7 to 11, and the total carbon number of the aromatic sulfonic acid is preferably 6 to 10. Applicable aromatic acids include, for example, salicylic acid (pKa: 3.0), phthalic acid (pKa: 2.9), terephthalic acid (pKa: 3.5), and benzenesulfonic acid (pKa: -2.0). , para-toluenesulfonic acid (pKa: -2.8), 1-naphthalenesulfonic acid (pKa: 0.2), 2-naphthalenesulfonic acid (pKa: 0.3), and the like.
Among aromatic carboxylic acids and aromatic sulfonic acids, aromatic sulfonic acids are preferred from the viewpoint of peeling performance, and para-toluenesulfonic acid is particularly preferred.

[Alkanolamine]
As the alkanolamine used in the present invention, any of primary alkanolamines, secondary alkanolamines, and tertiary alkanolamines can be used.
In the present invention, one kind of a plurality of alkanolamines can be used alone or two or more kinds can be used in combination.
The total carbon number of the alkanolamine is preferably 2 or more, more preferably 3 or more, and preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less, from the viewpoint of improving the peeling performance of the resin film. It is.

Examples of the primary alkanolamine include monoethanolamine, monopropanolamine, monoisopropanolamine, and monobutanolamine.
Examples of the secondary alkanolamine include diethanolamine, diisopropanolamine, N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, N-methylpropanolamine, and N-methylisopropanolamine. , N-ethylisopropanolamine, N-propylisopropanolamine and the like.
Examples of the tertiary alkanolamine include triethanolamine, triisopropanolamine, N,N-dimethylethanolamine, N,N-dimethylpropanolamine, N,N-diethylethanolamine, N-ethyldiethanolamine, and N-methyldiethanolamine. etc.

Among these, water-soluble alkanolamines having 2 to 6 carbon atoms are preferred, one or more selected from primary alkanolamines and secondary alkanolamines are more preferred, and monoethanolamine and diethanolamine are particularly preferred. , N-methylethanolamine, and diethanolamine is more preferred from the viewpoint of peeling performance.

By mixing the above-mentioned aromatic acid and alkanolamine, the stripping agent of the present invention consisting of a salt of these two components is produced.
When mixing alkanolamine and aromatic acid, the molar ratio expressed by alkanolamine/aromatic acid is preferably 0.5 to 10.0, more preferably 1.5 to 5.0. . If the molar ratio is less than 0.5, it may be difficult to obtain good resin film removal performance. Furthermore, if the molar ratio is greater than 10.0, the pH of the chemical solution becomes strongly alkaline, which may limit the environment in which it can be used.

The stripping agent of the present invention has a liquid property in a neutral to weakly alkaline range, and preferably has a pH range of 6.0 or more and less than 11.0, and the pH is preferably 7.0 or more and less than 11.0. is more preferable, and it is particularly preferable that pH=8.0 or more and 10.0 or less.
As a method for adjusting the liquid properties of the stripping agent of the present invention, the liquid properties can be made neutral or alkaline by adjusting the mixed molar ratio of alkanolamine and aromatic acid within the above range.

Generally, the stripping agent of the present invention is prepared by diluting a salt of an aromatic acid and an alkanolamine with water to an appropriate concentration to form an aqueous solution, and then using the resulting water-based stripping agent in the resin film stripping process. be. Further, the aqueous stripping agent of the present invention may be prepared by mixing an alkanolamine, an aromatic acid, and water. Examples of water include ion exchange water, distilled water, RO water, tap water, and industrial water.
Containing a salt of an aromatic acid selected from the group consisting of an aromatic carboxylic acid having 7 to 9 carbon atoms and an aromatic sulfonic acid having 5 to 8 carbon atoms and an alkanolamine having 2 to 10 carbon atoms in the stripper. The amount may be less than 50% by weight.
The content of water in the aqueous stripping agent is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more.
Further, the water-based stripping agent of the present invention may contain components that are generally blended in conventional resin film stripping agents for circuit boards. For example, surfactants, pH adjusters, water-soluble solvents, preservatives, anticorrosive agents, thickeners, colorants, etc. may be blended.

The release agent of the present invention is used to temporarily form a resin film on the surface of a circuit board during the manufacture of an electronic circuit board, and to remove the resin film from the surface after performing necessary processing steps. After forming a resin film on the surface of the circuit board using a removable resin film material and processing the circuit board, the resin film can be removed by bringing a release agent into contact with the resin film.
When manufacturing electronic circuit boards, it is important to protect the surface of the circuit board on which functional elements such as electronic circuits are first formed, that is, the main surface, from loads during processing in downstream processes. Therefore, in the present invention, a resin film is formed using a curable resin on the main surface of a circuit forming board, and after the necessary processing steps are performed, the resin film is removed from the main surface, thereby improving the board surface. can be protected.
In the present invention, the term "principal surface of the circuit-forming board" refers to the surface on which electronic circuits are first formed in the manufacturing process of the electronic circuit board. Furthermore, in the present invention, "the back surface of the circuit-forming board" means the surface opposite to the main surface.

The stripping agent of the present invention is suitably used to remove an alkali-soluble water-based resin film. The resin film material was a copolymer of styrene and maleic anhydride (molecular weight: 9500, product name: Poly (styrene/maleic anhydride) [copolymerization molar ratio = 75:25], manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). ) in 90 parts by weight of a 5% by weight aqueous ammonia solution and filtered through a filter with a pore size of 0.4 μm.
Further, as other resin film materials, polyimide resin compositions described in paragraphs 0011 to 0044 of JP-A-2019-131704 can be cited as an example.

Since a resin film is formed by applying the resin film material as described above to the main surface of the substrate and curing it, the main surface is protected during the step of processing the back surface of the substrate and the step of transporting the substrate. After the step in which it is necessary to protect the main surface of the substrate is completed, the resin film can be removed by bringing a release agent into contact with the resin film by dipping, spraying, or the like.
It is thought that the release agent dissolves or swells the resin film at the interface between the substrate and the resin film to reduce adhesion at the interface, thereby removing the resin film. Therefore, it is preferable to allow the release agent to sufficiently penetrate into the protective layer so that the release agent reaches the interface between the substrate and the resin film.
Further, when the release agent is brought into contact with the resin film, it is preferable that the temperature of the release agent is about 20 to 60°C.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.
1. Preparation of Stripping Agent A water-based resin film stripping agent for circuit boards was prepared by dissolving predetermined amounts of alkanolamine and aromatic acid in water and adjusting the total amount to 100% by mass using water. Table 1 shows the composition of the release agent prepared in each Example and Comparative Example.

2. Evaluation of release agents The release agents of Examples and Comparative Examples were evaluated as follows.
(1) Resin film peeling test a) Preparation of coating liquid Copolymer of styrene and maleic anhydride (molecular weight: 9500, product name: Poly (styrene/maleic anhydride) [copolymerization molar ratio = 75:25], Fuji A coating solution for forming a resin film was prepared by dissolving 5 parts by mass of Film (manufactured by Wako Pure Chemical Industries, Ltd.) in 90 parts by mass of a 5% by mass ammonia aqueous solution and filtering through a filter with a pore size of 0.4 μm. .

b) Formation of alkali-soluble resin film As electronic circuit boards, circular silicone wafers ("high-purity silicone wafers for research": manufactured by As One Co., Ltd., approximately 20 cm in diameter) and circular glass substrates ("dummy glass substrates": As One Co., Ltd.) were used. Co., Ltd., approximately 20 cm in diameter), the above resin film-forming coating liquid was applied onto each substrate. After placing about 0.5 g of the above coating liquid on the substrate, the coating was uniformly applied by rotating it for 80 seconds at 3000 rpm using a spin coater (product name "Opticoat MS-A150", manufactured by Mikasa Co., Ltd.). It was thermally cured for 10 minutes on a hot plate heated to 100° C. to form an alkali-soluble resin film with a thickness of 10 μm. Note that the weight of the coated resin film is recorded by weighing the substrate before and after coating.

c) Peeling test The circuit board coated with the resin film was placed in a glass Petri dish (about 25 cm in diameter), immersed in 100 g of a peeling agent, and left to stand for 1 minute. The circuit board after being left standing was immersed in ion-exchanged water, rinsed, and then dried at 80° C. for 1 hour. The liquid temperature during the peel test was adjusted to 40° C. and the test was conducted. This series of peeling steps was repeated three times.
From the mass of the circuit board before the start of the peeling test and the change in mass of the circuit board at the end of each peeling process, determine the amount of decrease in the mass of the resin film, and calculate the removal rate (%) of the resin film using the formula below. was calculated.

The peeling performance was evaluated by recording the number of peeling steps required until the removal rate of the resin film reached 100% or more.
Moreover, when the peeling process was completed three times, the appearance of the resin film after peeling was observed and evaluated.
The method for determining the peeling performance and the appearance of the peeling film are as follows.

<Method of determining peeling performance>
◎: Removal rate reached 100% in one peeling process.
○: Removal rate reached 100% after two or three peeling steps.
×: The removal rate did not reach 100% even after the peeling process was repeated three times.
<Method for determining the appearance of peeled resin film>
AA: The resin film that had peeled off and fallen off the substrate was completely dissolved and could not be observed with the naked eye.
A: Most of the resin film that had peeled off and fallen off the substrate had been dissolved.
B: The resin film that had peeled off and fallen off the substrate was not dissolved and remained in the form of sheets or fragments.

(2) Measurement of pH The pH of each stripping agent was measured using a pH meter (product name: LAQUA F-72, manufactured by Horiba, Ltd.). Note that the measurement temperature was 25°C, and the measurement was performed while stirring each release agent in a constant temperature bath at 25°C.

3. Evaluation Results The evaluation results are shown in Table 1.

(Evaluation results)
It was confirmed that the removers of Examples 1 to 3, Reference Example 4, and Example 5 had a high ability to remove the coated resin film even though the pH was neutral to weakly alkaline.

On the other hand, the release agents of Comparative Examples 1 and 2 do not have sufficient performance compared to the release agents of Examples 1 to 3, Reference Example 4, and Example 5.
Since the basic substance in the stripping agent of Comparative Example 1 was not an alkanolamine, the peeling performance of the resin film was not good, and the peeled resin film remained as a solid in the stripping agent.
Although the pKa of the acidic substance in the stripping agent of Comparative Example 2 was 4.0 or less, since it was not an aromatic acid, the peeling performance of the resin film was not good.

The resin film stripping agent for circuit boards of the present invention exhibits excellent stripping performance when removing by immersion an alkali-soluble water-based resin film coated on the main surface during the manufacturing process of electronic circuit boards. The resin film coated on the chip surface can be removed in a short time.
Although the stripping agent of the present invention has relatively mild liquid properties ranging from neutral to slightly alkaline, it is capable of removing resin films in a short time, and is capable of removing resin films on circuit boards. There are also few residual pieces.
Further, since the stripping agent of the present invention has a liquid property in the neutral to slightly alkaline range, it has little impact on the user and the environment in which it is used.
Furthermore, each component constituting the stripping agent of the present invention can be easily produced by industrial methods such as synthesis, which is advantageous in terms of production cost.

Claims (4)

Containing an aromatic acid selected from the group consisting of paratoluenesulfonic acid and terephthalic acid , a salt with diethanolamine as an alkanolamine , and water,
The content ratio of the alkanolamine diethanolamine and the aromatic acid selected from the group consisting of para-toluenesulfonic acid and terephthalic acid is 0.5 to 0.5 when expressed as a molar ratio of alkanolamine/aromatic acid. 10.0,
having a composition in which the water content is 60% by mass or more,
A resin film stripping agent for circuit boards used to peel a resin film formed on a board using a resin containing a copolymer of styrene and maleic anhydride . The resin film peeling for circuit boards according to claim 1 , wherein the content ratio of alkanolamine and aromatic acid is 1.5 to 5.0 when expressed as a molar ratio of alkanolamine/aromatic acid. agent. The resin film stripping agent for circuit boards according to claim 1 or 2 , having a pH value of 6 or more and less than 11. A step of forming a resin film on the main surface of a circuit board using a resin containing a copolymer of styrene and maleic anhydride, and a resin film for a circuit board according to any one of claims 1 to 3 . A method for manufacturing an electronic circuit board, including the step of removing the resin film by bringing a release agent into contact with the resin film.