JP2022042708A - Resin composition etching method - Google Patents

Abstract

To provide an etching method which can remove a resin composition layer containing a resin composition containing an alkali-insoluble resin and an inorganic filler without leaving residues, and prevent flowing of the resin composition layer in a heating and curing step, in process of removing the resin composition using an etchant.SOLUTION: A composition etching method includes: an etching step of performing etching on a resin composition containing an alkali-insoluble resin and 30-80 mass% of an inorganic filler using an etchant containing 15-45 mass% of an alkali metal hydroxide, 1-40 mass% of an ethanol amine compound and 3-60 mass% of a polyol compound; an ultrasonic irradiation step; an intermediate curing step of performing heating treatment at 85-95°C; and a heating curing step of performing heating treatment at 120-200°C.SELECTED DRAWING: None

Description

The present invention relates to a method for etching a resin composition containing an alkali-insoluble resin and 30 to 80% by mass of an inorganic filler.

In recent years, with the miniaturization and higher performance of electronic devices, there is a strong demand for the formation of fine wiring and the reduction of the coefficient of thermal expansion in circuit boards. Among them, as a means for reducing the thermal expansion coefficient of the insulating material, a method of increasing the filling of the insulating material, that is, increasing the content of the inorganic filler in the insulating material is known. Further, it has been proposed to use an alkali-insoluble resin which contains an epoxy resin, a phenol novolac-based curing agent, a phenoxy resin, a cyanate resin and the like as an insulating material and has excellent moisture resistance. The insulating resin composition containing these inorganic fillers and an alkali-insoluble resin has excellent physical properties such as heat resistance, dielectric properties, mechanical strength, and chemical resistance, and is a solder used for the outer layer surface of a circuit board. It is widely used as an interlayer insulating material used for resists and multilayer build-up wiring boards.

FIG. 1 is a schematic cross-sectional structural diagram of a solder resist pattern in which a portion other than the connection pad 3 to be soldered on the circuit board is covered with the resin composition layer 4. The structure shown in FIG. 1 is called an SMD (Solder Masked Defined) structure, and is characterized in that the opening of the resin composition layer 4 is smaller than that of the connection pad 3. The structure shown in FIG. 2 is called an NSMD (Non Solder Masked Defined) structure, and is characterized in that the opening of the resin composition layer 4 is larger than that of the connection pad 3.

The opening of the resin composition layer 4 in FIG. 1 is formed by removing a part of the resin composition layer. As a processing method for removing the resin composition layer containing the resin composition containing the inorganic filler and the alkali-insoluble resin, a known method such as a drill, a laser, a plasma, or a blast can be used. Moreover, these methods can be combined as needed. Among them, processing by a laser such as a carbon dioxide laser, an excimer laser, a UV laser, or a YAG laser is the most common, and a part of the resin composition layer 4 is removed by laser light irradiation to form a through hole for forming a through hole. , Through holes and non-through holes such as an opening for forming a via hole and an opening for forming a connection pad 3 can be formed (see, for example, Patent Documents 1 and 2).

However, processing by irradiation with laser light requires a large number of shots, for example, when a carbon dioxide laser is used, and as post-treatment, desmear treatment is performed using an oxidizing agent consisting of an aqueous solution such as chromic acid or permanganate. Need to be done. Further, when an excimer laser is used, the processing time becomes very long. Furthermore, the UV-YAG laser has an advantage over other laser beams in that it can perform microfabrication, but it removes not only the resin composition layer but also the metal layer existing in the vicinity at the same time. There was a problem.

Further, when the laser beam is applied to the resin composition layer, the light energy is absorbed by the object at the irradiation site, and the object excessively generates heat according to the specific heat. In some cases, such defects may occur. Further, it has been proposed to use a thermosetting resin in the resin composition layer in response to this heat generation, but if a thermosetting resin is used, cracks may easily occur in the resin composition layer. ..

As a method other than laser light irradiation, a method of removing the resin composition layer by a wet blast method can be mentioned. A resin composition layer is formed on a circuit board having a connection pad on an insulating substrate, then cured, and a resin layer for forming a wet blast mask is provided on the resin composition layer. By exposing and developing, a patterned wet blast mask is formed. Then, the resin composition layer is removed by performing wet blasting to form an opening, and subsequently, the mask for wet blasting is removed (see, for example, Patent Document 3).

However, in the processing by wet blasting, the thickness that can be polished by one blasting treatment is small, and it is necessary to repeat the blasting treatment a plurality of times. Therefore, not only the time required for polishing becomes very long, but also the portion to which the resin composition layer is adhered is uniform depending on the material, such as on the connection pad or on the insulating substrate. It was extremely difficult to perform high-precision processing because it could not be polished properly and residue was generated.

As a processing method for removing a resin composition layer containing a resin composition containing an inorganic filler and an alkali-insoluble resin, an etching method performed by an immersion treatment using a hydrazine-based chemical solution at 40 ° C. as an etching solution is disclosed. (See, for example, Patent Document 4). However, hydrazine is a toxic substance and is not preferable because it has a large effect on the human body and has a large environmental load.

Further, an etching method using an etching solution containing 15 to 45% by mass of an alkali metal hydroxide is disclosed (see, for example, Patent Document 5). In Patent Document 5, as a more preferable embodiment, an etching solution further containing an ethanolamine compound is also disclosed.

Although the etching solution of Patent Document 5 has a small effect on the human body and an environmental load, a residue may appear on the surface after etching. In addition, undercuts may be seen in the resin composition layer after etching. In addition, in high-productivity etching processing, it is important to arrange several patterns in the plane and process each pattern uniformly, but due to the recent increase in the density of the substrate, it is more than ever. Fine processing has been required, and its uniformity has also been required at the same time, which may not be sufficient in some cases.

The resin composition layer containing the resin composition containing the inorganic filler and the alkali-insoluble resin can be stably removed without any residue, and the resin composition layer after etching is less likely to undercut. As an etching method with high uniformity, it contains 15 to 45% by mass of alkali metal hydroxide as the first component and 1 to 40% by mass of the ethanolamine compound as the second component, and as the third component. Disclosed is an etching method comprising an etching step using an etching solution containing 3 to 60% by mass of a polyol compound, 2 to 20% by mass of a polyvalent carboxylic acid or 2 to 20% by mass of a hydroxy acid (for example). , Patent Documents 6 and 7). Further, an etching method including an ultrasonic irradiation step of irradiating ultrasonic waves after the etching step is also disclosed. Patent Documents 6 and 7 disclose that the alkali-insoluble resin is, for example, a resin containing an epoxy resin and a heat-curing agent that cures the epoxy resin.

The etched resin composition layer is usually subjected to a heat curing step at a temperature of 160 ° C to 200 ° C. By the heat curing step, the resin composition layer is heat-cured by the thermosetting agent. However, when the resin composition layer etched by the etching method disclosed in Patent Documents 6 and 7 is subjected to a heat curing step, the resin composition layer may flow and diffuse on the side surface or the upper surface of the connection pad. there were. Therefore, there has been a demand for an etching method in which the resin composition layer does not flow during the heat curing step.

Japanese Patent Application Laid-Open No. 2003-101244 International Publication No. 2017/38713 Pamphlet Japanese Unexamined Patent Publication No. 2008-300691 International Publication No. 2018/88345 Pamphlet International Publication No. 2018/186362 Pamphlet International Publication No. 2020/158610 Pamphlet International Publication No. 2020/08447 Pamphlet

The present invention provides a method for etching a resin composition in which the resin composition layer does not flow during a heat curing step in a process of removing an alkali-insoluble resin and a resin composition containing an inorganic filler using an etching solution. Is the issue.

The present inventors have found that the above problems can be solved by the following means.

A resin composition containing an alkali-insoluble resin and 30 to 80% by mass of an inorganic filler is mixed with 15 to 45% by mass of an alkali metal hydroxide, 1 to 40% by mass of an ethanolamine compound, and 3 to 60% by mass of a polyol compound. It is characterized by having at least an etching step using an etching solution containing the above, an ultrasonic irradiation step, an intermediate curing step of heat treatment at 85 to 95 ° C., and a heat curing step of heat treatment at 120 to 200 ° C. A method for etching the resin composition.

According to the present invention, there is a method for etching a resin composition in which the resin composition layer does not flow during a heat curing step in a process of removing an alkali-insoluble resin and a resin composition containing an inorganic filler using an etching solution. Can be provided.

It is a schematic cross-sectional structure diagram of a solder resist pattern. It is a schematic cross-sectional structure diagram of a solder resist pattern. It is sectional drawing which showed an example of the process of etching the resin composition layer 4 by the etching method of this invention.

Hereinafter, embodiments for carrying out the present invention will be described. In addition, in this specification, "etching method of resin composition" may be abbreviated as "etching method".

The etching method of the present invention is used for processing to remove a resin composition containing an alkali-insoluble resin and an inorganic filler of 30 to 80% by mass using an etching solution.

The etching solution used in the present invention is an alkaline aqueous solution containing 15 to 45% by mass of an alkali metal hydroxide. Since the alkali-insoluble resin has the property of not being dissolved in the alkaline aqueous solution, it cannot be originally removed by the alkaline aqueous solution. However, by using the etching solution used in the present invention, the resin composition containing the alkali-insoluble resin can be removed. This is because the inorganic filler in the highly filled resin composition, that is, the inorganic filler filled in the resin composition with a high content of 30 to 80% by mass, has a high concentration of alkali metal hydroxide. This is because it is dissolved, dispersed and removed by an aqueous solution containing.

When the content of the alkali metal hydroxide is 15% by mass or more, the solubility of the inorganic filler is excellent, and when the content of the alkali metal hydroxide is 45% by mass or less, the precipitation of the alkali metal hydroxide The liquid is excellent in stability over time because it is unlikely to occur. The content of the alkali metal hydroxide is more preferably 20 to 45% by mass.

As the alkali metal hydroxide, at least one compound selected from the group of potassium hydroxide, sodium hydroxide and lithium hydroxide is preferably used. As the alkali metal hydroxide, one of these may be used alone, or two or more of them may be used in combination.

The etching solution used in the present invention contains 1 to 40% by mass of an ethanolamine compound. When the etching solution contains the ethanolamine compound, the ethanolamine compound permeates into the resin composition, the resin composition is swollen, and the inorganic filler can be uniformly dissolved. When the content of the ethanolamine compound is 1% by mass or more, the swelling property of the alkali-insoluble resin is excellent, and when it is 40% by mass or less, the compatibility with water is high, phase separation is difficult to occur, and stability over time. Excellent for. The content of the ethanolamine compound is more preferably 3 to 35% by mass.

The ethanolamine compound may be of any kind such as a primary amine, a secondary amine, or a tertiary amine, and may be used alone or in combination of two or more. good. An example of a typical amine compound is 2-aminoethanol, which is a primary amine; a mixture of a primary amine and a secondary amine (that is, a primary amino group and a secondary amino in one molecule). 2- (2-Aminoethylamino) ethanol which is a compound having a group); 2- (methylamino) ethanol which is a secondary amine, 2- (ethylamino) ethanol; 2,2 which is a tertiary amine ′ -Methyliminodiethanol (also known as N-methyl-2,2′-iminodiethanol), 2,2′-ethyliminodiethanol (also known as N-ethyl-2,2′-iminodiethanol), 2- (dimethylamino) ) Ethanol, triethanolamine and the like can be mentioned. Of these, 2-aminoethanol and 2- (2-aminoethylamino) ethanol are more preferable.

The etching solution used in the present invention contains 3 to 60% by mass of a polyol compound. By containing the polyol compound in the etching solution, the alkali-insoluble resin and the dissolved inorganic filler can be dispersed and removed at the same time.

The mechanism of this effect is beyond speculation, but it is believed to be related to the above-mentioned dissolution / dispersion removal mechanism of this etching solution. In order to stably remove the resin composition by etching, a part or all of the highly filled inorganic filler in the resin composition is dissolved in an etching solution containing a high concentration of alkali metal hydroxide. It is necessary to remove the alkali-insoluble resin and the dissolved inorganic filler at the same time when the film shape as the resin composition cannot be maintained. If the removal of only one of them proceeds, the other component becomes a residue and remains on the surface after etching. It is considered that the etching solution contains a polyol compound, a polyvalent carboxylic acid or a hydroxy acid, so that it has a function of collecting components that cannot maintain the film shape and at the same time improves the performance of removing them. It is considered that this effect increases the margin of the treatment time in which no residue remains, and can stably remove the resin composition containing the alkali-insoluble resin and many inorganic fillers.

If the content of the polyol compound used in the etching solution used in the present invention is less than 3% by mass, the ability to disperse all together becomes insufficient, and if it exceeds 60% by mass, it is too cohesive and removed. Insufficient sex. The content of the polyol compound is more preferably 10 to 40% by mass.

The polyol compound used in the etching method of the present invention has a preferable molecular weight range, preferably 80 or more and 200 or less. Further, as the polyol compound, a compound having three or more hydroxyl groups is more preferable. Specific examples include glycerin, pentaerythritol, sorbitol, xylitol and the like. Of these, glycerin is particularly preferable. Further, as the polyol compound, one kind may be used alone, or two or more kinds may be used in combination.

A coupling agent, a leveling agent, a colorant, a surfactant, a defoaming agent, an organic solvent and the like can be appropriately added to the etching solution used in the present invention, if necessary. Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone and cyclohexanone; acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate and carbitol acetate; carbitols such as cellosolve and butyl carbitol; Aromatic hydrocarbons such as toluene and xylene; amide-based solvents such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone can be mentioned.

The etching solution used in the present invention is preferably an alkaline aqueous solution. As the water used for the etching solution used in the present invention, tap water, industrial water, pure water and the like can be used. Of these, pure water is preferably used, and pure water generally used for industrial purposes can be used.

The etching solution used in the present invention is an etching solution of a resin composition containing an alkali-insoluble resin and an inorganic filler. The content of the inorganic filler in the resin composition is 30 to 80% by mass with respect to 100% by mass of the non-volatile content in the resin composition. When the content of the inorganic filler is less than 30% by mass, the etching does not proceed because the amount of the inorganic filler as a site dissolved by the etching solution is too small with respect to the entire resin composition. When the content of the inorganic filler exceeds 80% by mass, the flexibility tends to decrease due to the decrease in the fluidity of the resin composition, which is inferior in practicality.

In the present invention, examples of the inorganic filler include silicates such as silica, glass, clay and mica; oxides such as alumina, magnesium oxide, titanium oxide and silica; carbonates such as magnesium carbonate and calcium carbonate; water. Hydroxides such as aluminum oxide, magnesium hydroxide and calcium hydroxide; sulfates such as barium sulfate and calcium sulfate can be mentioned. Further, examples of the inorganic filler include aluminum borate, aluminum nitride, boron nitride, strontium titanate, barium titanate and the like. Among these, at least one compound selected from the group consisting of silica, glass, clay and aluminum hydroxide is more preferably used because it has high solubility in an etching solution. Silica is more preferable because it has excellent low thermal expansion property, and spherical fused silica is particularly preferable. As the inorganic filler, one of these may be used alone, or two or more of them may be used in combination.

The resin composition according to the present invention may contain an organic filler in addition to the inorganic filler. When the organic filler is contained, the content of the organic filler is preferably about 5 to 30% by mass with respect to 100% by mass of the non-volatile content in the resin composition. Examples of the organic filler include polytetrafluoroethylene (PTFE), fluoroethylene-propylene copolymer (FEP), perfluoroalkoxy polymer (PFA), polychlorotrifluoroethylene (PCTFE), and tetrafluoroethylene-. Examples thereof include at least one fluororesin selected from the group consisting of chlorotrifluoroethylene copolymer (TFE / CTFE) and ethylene-chlorotrifluoroethylene copolymer (ECTFE). One of these resins may be used alone, or two or more of these resins may be used in combination.

The alkali-insoluble resin in the present invention will be described. The alkali-insoluble resin is not particularly limited except that it is not dissolved or dispersed in an aqueous alkaline solution. Specifically, it is a resin having a very small content of a carboxyl group-containing resin or the like required for dissolving in an alkaline aqueous solution, and has an acid value (JIS K2501) which is an index of the content of free carboxyl groups in the resin. : 2003) is preferably less than 40 mgKOH / g. More specifically, the alkali-insoluble resin is a resin containing an epoxy resin and a thermosetting agent that cures the epoxy resin. Examples of the alkaline aqueous solution include an aqueous solution containing an inorganic alkaline compound such as an alkali metal silicate, an alkali metal hydroxide, an alkali metal phosphate, an alkali metal carbonate, an ammonium phosphate, and an ammonium carbonate, and a monoethanolamine. Diethanolamine, triethanolamine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, trimethyl-2-hydroxyethylammonium hydroxide (choline), etc. Examples thereof include an aqueous solution containing the organic alkaline compound of.

Examples of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; novolak type epoxy resins such as phenol novolac type epoxy resin and cresol novolak type epoxy resin. Can be mentioned. Further, examples of the epoxy resin include biphenyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, phenoxy type epoxy resin, fluorene type epoxy resin and the like. As the epoxy resin, one of these may be used alone, or two or more of them may be used in combination.

The thermosetting agent is not particularly limited as long as it has a function of curing the epoxy resin, but preferred ones are a phenol-based curing agent, a naphthol-based curing agent, an active ester-based curing agent, a benzoxazine-based curing agent, and the like. Examples thereof include cyanate ester resin. As the thermosetting agent, one of these may be used alone, or two or more thereof may be used in combination.

In addition to the above curing agent, a curing accelerator can be further contained. Examples of the curing accelerator include an organic phosphine compound, an organic phosphonium salt compound, an imidazole compound, an amine adduct compound, and a tertiary amine compound. As the curing accelerator, one of these may be used alone, or two or more thereof may be used in combination. When a cyanate ester resin is used as a thermosetting agent, an organic metal compound used as a curing catalyst may be added for the purpose of shortening the curing time. Examples of the organometallic compound include an organocopper compound, an organozinc compound, an organocobalt compound and the like.

The resin composition containing an alkali-insoluble resin and an inorganic filler can form an insulating resin composition layer by thermosetting, but the etching in the etching method of the present invention is performed in the A stage (before the start of the curing reaction) or. It proceeds in the state of B stage (intermediate stage of curing reaction). Even in the A stage or the B stage, the alkali-insoluble resin is not dissolved in the etching solution, but the inorganic filler is partially or completely dissolved by the etching solution, so that the dispersion removal of the resin composition proceeds. In the C stage and the resin is completely cured, it becomes difficult for the etching solution to swell the resin composition layer and permeate into the resin composition layer, which makes uniform etching difficult.

The thermosetting conditions from the A stage to the B stage are preferably 80 to 160 ° C. for 10 to 90 minutes, and more preferably 80 to 90 ° C. for 40 to 90 minutes, but are limited thereto. It's not a thing. When heated at a high temperature exceeding 160 ° C., thermosetting further progresses, and the etching process using an etching solution becomes difficult.

The etching method of the present invention will be described below. FIG. 3 is a cross-sectional process diagram showing an example of a step of etching the resin composition layer 4 by the etching method of the present invention. In this etching method, a solder resist pattern in which a part or all of the solder connection pad 3 on the circuit board is exposed from the resin composition layer 4 can be formed.

In the step (I), the conductor pattern A is formed by patterning the copper foil 3'on the surface of the copper-clad laminate 1'consisting of the insulating layer 2 and the copper foil 3'by etching, and the solder connection pad 3 is formed. The circuit board 1 to have is formed.

In the step (II), the resin composition layer 4 with the copper foil 6 is formed on the surface of the circuit board 1 so as to cover the entire surface.

In the step (III), the copper foil 6 on the resin composition layer 4 is patterned by etching to form a metal mask as the etching resist 5.

In step (IV), the resin composition layer 4 is etched through the etching resist 5 (metal mask) with the etching solution for the resin composition layer until a part or all of the solder connection pad 3 is exposed.

In the step (V), the etching resist 5 (metal mask) is removed by etching to form a solder resist pattern in which a part or all of the solder connection pad 3 is exposed from the resin composition layer 4.

In the etching method of the present invention, the temperature of the etching solution is preferably 50 to 90 ° C. The optimum temperature varies depending on the type of resin composition, the thickness of the resin composition layer containing the resin composition, the shape of the pattern obtained by the process of removing the resin composition, etc., but the temperature of the etching solution is higher. The temperature is preferably 50 to 80 ° C, more preferably 50 to 70 ° C.

In the resin composition etching method of the present invention, a part or all of the highly filled inorganic filler is gradually dissolved from the surface layer of the resin composition and dispersed together with the alkali-insoluble resin to form the resin composition. Removal proceeds.

In the etching method of the present invention, methods such as dipping treatment, paddle treatment, spray treatment, brushing, and scraping can be used for the treatment of etching the resin composition. Of these, the dipping treatment is preferable.

In the etching method of the present invention, after the resin composition is removed by an etching treatment, the etching solution remaining on the surface of the resin composition is washed by a water washing treatment. As a method of washing with water, a spray method is preferable from the viewpoint of diffusion rate and uniformity of liquid supply. As the washing water, tap water, industrial water, pure water or the like can be used. Of these, it is preferable to use pure water. As the pure water, those generally used for industrial purposes can be used. The temperature of the washing water is not less than the temperature of the etching solution, and the temperature difference is preferably 20 to 30 ° C.

The etching method of the present invention includes a step of irradiating ultrasonic waves after an etching process using the above etching solution. The step of irradiating ultrasonic waves may be a water washing step immediately after the etching treatment, or ultrasonic irradiation is performed during the step of removing the etching resist 5 which is carried out after the etching treatment, the washing step, and the drying step. May be done. Further, even if ultrasonic irradiation is performed in the washing step after removing the etching resist 5, it works effectively. However, even if ultrasonic irradiation is performed during the etching process, the desired effect cannot be obtained. Among the steps (I) to (V) described above, the etching method of the present invention refers to the steps from (III) to (V) completed to the next step. Then, in the ultrasonic wave irradiation step according to the present invention, ultrasonic wave irradiation is performed in a wet manner from the end of the etching process with the etching solution of (IV) to the end of (V) and the start of the next step. Refers to the process.

It is considered that the reason why the desired effect is not obtained even if ultrasonic irradiation is performed during the etching process is related to the dissolution / dispersion removal mechanism of the etching method of the present invention. In the etching mechanism of the present invention, a part or all of the inorganic filler highly filled in the resin composition insoluble in the etching solution is dissolved in the etching solution containing a high concentration of alkali metal hydroxide. It is an etching method in which a state in which the film shape as a resin composition cannot be maintained is formed, and a portion where the film cannot be formed is removed in a subsequent step. Therefore, it is considered that ultrasonic irradiation in the etching solution causes the shape to be distorted after etching and the in-plane uniformity cannot be maintained, which causes the desired effect to not be obtained.

The conditions for ultrasonic irradiation vary depending on the composition and curing state of the resin composition containing the alkali-insoluble resin and 30 to 80% by mass of the inorganic filler, the composition of the etching solution, etc., but a frequency of 15 kHz or higher is preferable. , 50 kHz or higher is more preferable. The liquid temperature at the time of irradiating ultrasonic waves is preferably 70 ° C. or lower, more preferably 60 ° C. or lower.

As the etching resist 5 used in the etching process, a dry film resist pattern can be used in addition to the metal mask described above.

The dry film resist according to the present invention contains at least a photocrosslinkable resin composition, and a photocrosslinkable resin is coated on a carrier film such as polyester to form a photocrosslinkable resin layer, and in some cases, protection of polyethylene or the like. The structure is such that the photocrosslinkable resin layer is covered with a film. The photocrosslinkable resin layer contains, for example, a binder polymer containing a carboxyl group, a photopolymerizable compound having at least one polymerizable ethylenically unsaturated group in the molecule, a photopolymerization initiator, a solvent, and other additives. do. The blending ratio thereof is determined by the balance of required properties such as sensitivity, resolution, and degree of cross-linking. Examples of photocrosslinkable resin compositions are "Photopolymer Handbook" (edited by Photopolymer Association, published in 1989, published by Industrial Research Institute Co., Ltd.) and "Photopolymer Technology" (edited by Ao Yamamoto and Mototaro Nagamatsu, 1988). It is described in publication, Nikkan Kogyo Shimbun, etc.), and a desired photocrosslinkable resin composition can be used. The thickness of the photocrosslinkable resin layer is preferably 15 to 100 μm, more preferably 20 to 50 μm.

As the exposure method of the dry film resist according to the present invention, a xenon lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, a reflected image exposure using a UV fluorescent lamp as a light source, a single-sided or double-sided close contact exposure using a photomask, or a proxy. Examples include the Miti method, the projection method, and laser scanning exposure. When scanning exposure is performed, a laser light source such as a He-Ne laser, a He-Cd laser, an argon laser, a krypton ion laser, a ruby laser, a YAG laser, a nitrogen laser, a dye laser, or an excima laser is used according to the emission wavelength. It can be exposed by scanning exposure after converting the wavelength, or by scanning exposure using a liquid crystal shutter or a micromirror array shutter.

As a method for developing a dry film resist according to the present invention, an unnecessary drying film resist (unexposed) is sprayed from the vertical direction of the substrate toward the surface of the substrate by using a developing solution suitable for the photoresist resin layer to be used. Part) is removed to form an etching resist 5 composed of a dry film resist pattern. As the developing solution, generally 1 to 3% by mass of an aqueous sodium carbonate solution is used, and more preferably 1% by mass of an aqueous sodium carbonate solution is used.

As a method for peeling the dry film resist pattern used as the etching resist 5, a stripping solution suitable for the photoresist resin layer to be used is used, and the dry film resist pattern is sprayed from the vertical direction of the substrate toward the substrate surface. Remove. As the stripping solution, generally 2 to 4% by mass of a sodium hydroxide aqueous solution is used, and more preferably 3% by mass of a sodium hydroxide aqueous solution is used.

In the etching method of the present invention, an intermediate curing step is performed before the heat curing step of the resin composition layer. By performing the intermediate curing step, the flow of the resin composition layer generated during the heat curing step of the resin composition layer can be suppressed. By setting the intermediate cure temperature at 85 to 95 ° C., the flow of the resin composition layer in the intermediate cure step and the flow of the resin composition layer in the heat curing step can be suppressed. The intermediate curing step is preferably carried out for 20 minutes or more.

In the etching method of the present invention, a heat curing step is performed after the intermediate curing step of the resin composition layer. By performing the heat curing step, the resin composition layer can be completely heat-cured to obtain a film having high insulation reliability. The temperature in the heat curing step is 120 to 200 ° C., more preferably 130 ° C. or higher. This temperature range allows the resin composition layer to be completely thermoset. The heat curing step is preferably performed in the range of 5 to 120 minutes.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to this example.

(Examples 1 to 6)
78% by mass of spherical molten silica as an inorganic filler, 10% by mass of a biphenyl aralkyl type epoxy resin as an epoxy resin, 10% by mass of a phenol novolac type cyanate resin as a thermosetting agent, and 1% by mass of triphenylphosphine as a curing accelerator. In addition, a coupling agent and a leveling agent were added, and the total amount was 100% by mass, and the mixture was mixed with methyl ethyl ketone and cyclohexanone as a medium to obtain a liquid resin composition.

Next, the liquid resin composition was applied onto a polyethylene terephthalate film (thickness 38 μm) and then dried at 100 ° C. for 5 minutes to remove the medium. As a result, an A-stage resin composition layer composed of a resin composition containing an alkali-insoluble resin and an inorganic filler was formed with a film thickness of 20 μm.

Subsequently, a peelable metal foil in which a copper foil 6 having a thickness of 3 μm, a peeling layer, and a carrier foil are laminated in this order is prepared, and the copper foil 6 and the resin composition layer 4 are thermocompression bonded so as to be in contact with each other. After that, the peeling layer and the carrier foil were peeled off to obtain a resin composition layer 4 with a copper foil 6.

The copper foil 3'on one surface of the epoxy resin glass cloth base copper-clad laminate 1'(area 170 mm x 255 mm, copper foil thickness 12 μm, base material thickness 0.1 mm) is patterned by etching to form a conductor pattern A. The formed epoxy resin glass cloth base material (circuit board 1) was obtained. Next, the polyethylene terephthalate film was peeled off from the resin composition layer 4 with the copper foil 6, and the pressure was set to 100 ° C. using a vacuum thermocompression bonding laminator on the epoxy resin glass cloth base material on which the conductor pattern A was formed. After vacuum thermocompression bonding at 1.0 MPa, it was heated at 90 ° C. for 45 minutes to form the resin composition layer 4 of the B stage.

Subsequently, the copper foil 6 on the resin composition layer 4 was patterned by etching to form an opening in a predetermined region of the copper foil, and the resin composition layer 4 with the etching resist 5 (metal mask) was prepared.

Next, the resin composition layer 4 was subjected to an etching treatment by an immersion treatment at 60 ° C. for 40 seconds with the etching solution shown in Table 1 via the etching resist 5. After the etching treatment, the etching solution remaining on the surface of the resin composition layer 4 was washed by a dipping treatment with pure water. During this immersion treatment, ultrasonic irradiation was performed. Then, the surface was washed by spraying with pure water.

Next, the intermediate curing step was performed on the etched resin composition layer 4 at the temperatures shown in Table 1 for 30 minutes, and then the presence or absence of flow of the resin composition layer 4 in the intermediate curing step was observed with an optical microscope. The results are shown in Table 1. Then, the resin composition layer 4 was heat-cured at 180 ° C. for 90 minutes, and then the flow of the resin composition layer 4 in the heat-curing step was observed with an optical microscope as shown in Table 1. ..

(Flow of resin composition layer)
◯: There is no flow of the resin composition layer 4.
Δ: The resin composition layer 4 is diffused on the side surface of the conductor pattern due to the flow.
X: The resin composition layer 4 is diffused on the side surface and the upper surface of the conductor pattern due to the flow.

(Examples 7 to 12)
Spherical molten silica 35% by mass as an inorganic filler, biphenyl aralkyl type epoxy resin 30% by mass as an epoxy resin, phenol novolac type cyanate resin 30% by mass as a thermosetting agent, and triphenylphosphine 3% by mass as a curing accelerator. In addition, a coupling agent and a leveling agent were added, and the total amount was 100% by mass, and the mixture was mixed with methyl ethyl ketone and cyclohexanone as a medium to obtain a liquid resin composition.

Next, the liquid resin composition was applied onto a polyethylene terephthalate film (thickness 38 μm) and then dried at 100 ° C. for 5 minutes to remove the medium. As a result, an A-stage resin composition layer composed of a resin composition containing an alkali-insoluble resin and an inorganic filler was formed with a film thickness of 20 μm.

Subsequently, a peelable metal foil in which a copper foil 6 having a thickness of 3 μm, a peeling layer, and a carrier foil are laminated in this order is prepared, and the copper foil 6 and the resin composition layer 4 are thermocompression bonded so as to be in contact with each other. After that, the peeling layer and the carrier foil were peeled off to obtain a resin composition layer 4 with a copper foil 6.

The copper foil 3'on one surface of the epoxy resin glass cloth base copper-clad laminate 1'(area 170 mm x 255 mm, copper foil thickness 12 μm, base material thickness 0.1 mm) is patterned by etching to form a conductor pattern A. The formed epoxy resin glass cloth base material (circuit board 1) was obtained. Next, the polyethylene terephthalate film was peeled off from the resin composition layer 4 with the copper foil 6, and the pressure was set to 100 ° C. using a vacuum thermocompression bonding laminator on the epoxy resin glass cloth base material on which the conductor pattern A was formed. After vacuum thermocompression bonding at 1.0 MPa, it was heated at 90 ° C. for 45 minutes to form the resin composition layer 4 of the B stage.

Subsequently, the copper foil 6 on the resin composition layer 4 was patterned by etching to form an opening in a predetermined region of the copper foil, and the resin composition layer 4 with the etching resist 5 (metal mask) was prepared.

Next, the resin composition layer 4 was subjected to an etching treatment by an immersion treatment at 60 ° C. for 40 seconds with the etching solution shown in Table 1 via the etching resist 5. After the etching treatment, the etching solution remaining on the surface of the resin composition layer 4 was washed by a dipping treatment with pure water. During this immersion treatment, ultrasonic irradiation was performed. Then, the surface was washed by spraying with pure water.

Next, the intermediate curing step was performed on the etched resin composition layer 4 at the temperatures shown in Table 1 for 30 minutes, and then the presence or absence of flow of the resin composition layer 4 in the intermediate curing step was observed with an optical microscope. The results are shown in Table 1. Then, the resin composition layer 4 was heat-cured at 180 ° C. for 90 minutes, and then the presence or absence of flow of the resin composition layer 4 in the heat-curing step was observed with an optical microscope. The results are shown in Table 1.

As can be seen from the results in Table 1, the present invention can perform the heat curing step without flowing the resin composition layer as compared with the comparative example.

The etching solution and etching method of the present invention can etch an insulating resin composition layer having a high content of an inorganic filler and having excellent heat resistance, dielectric properties, mechanical strength, chemical resistance, and the like. It can be applied to, for example, fine processing of insulating resin in a multi-layer build-up wiring board, a module board with built-in components, a flip chip package board, a motherboard for mounting a package board, and the like.

1 Circuit board 1'Copper laminated board 2 Insulation layer 3 Solder connection pad, Connection pad 3'Copper foil 4 Resin composition layer 5 Etching resist (metal mask, dry film resist pattern)
6 Copper foil, dry film resist 7 Evaluation part A Conductor pattern

Claims (1)

A resin composition containing an alkali-insoluble resin and 30 to 80% by mass of an inorganic filler is mixed with 15 to 45% by mass of an alkali metal hydroxide, 1 to 40% by mass of an ethanolamine compound, and 3 to 60% by mass of a polyol compound. It is characterized by having at least an etching step using an etching solution containing the above, an ultrasonic irradiation step, an intermediate curing step of heat treatment at 85 to 95 ° C., and a heat curing step of heat treatment at 120 to 200 ° C. A method for etching the resin composition.

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