JP2021019079A - Etching method for resin composition - Google Patents

Abstract

To provide an etching method of a resin composition can remove a resin composition layer containing a resin composition without residue and that has high in-plane uniformity and high productivity in a process of removing an alkali-insoluble resin and a resin composition containing an inorganic filler using an etching solution.SOLUTION: In an etching method of a resin composition for etching a resin composition containing an alkali-insoluble resin and an inorganic filler of 50 to 80 mass% with an etching solution containing an alkali metal hydroxide of 15 to 45 mass%, a time from the end of the etching process to a subsequent washing process is within 30 seconds.SELECTED DRAWING: None

Description

The present invention relates to an etching method for a resin composition containing an alkali-insoluble resin and 50-80% 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 lowering the coefficient of thermal expansion 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 containing an epoxy resin, a phenol novolac-based curing agent, a phenoxy resin, a cyanate resin and the like as an insulating material and having excellent moisture resistance. The insulating resin composition containing these inorganic fillers and 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 multi-layer build-up wiring boards.

FIG. 1 is a schematic cross-sectional structural view 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 connecting 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 with a laser such as a carbon dioxide gas 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, in the processing by irradiation with laser light, for example, when a carbon dioxide laser is used, a large number of shots are required, and as a post-treatment, a 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 resin composition layer is irradiated with laser light, light energy is absorbed by the object at the irradiated portion, and the object generates heat excessively according to the specific heat, and the heat generation causes melting, deformation, alteration, and discoloration of the resin. 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 when the 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 blasting mask is provided on the resin composition layer. By exposing and developing, a patterned wet blasting 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 was not possible to perform proper polishing 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 not preferable because it is a poison and 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). Patent Document 5 also discloses an etching solution further containing an ethanolamine compound as a more preferable embodiment. Although the etching solution of Patent Document 5 has a small effect on the human body and an environmental load, there are cases where a residue appears on the surface after etching and undercuts are observed in the resin composition layer after etching. In addition, in highly productive etching processing, it is important to arrange a number of 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 is required, and its uniformity is also required at the same time, which may not be sufficient in some cases.

Japanese Unexamined Patent Publication 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

In the process of removing the resin composition containing the alkali-insoluble resin and the inorganic filler using an etching solution, the resin composition layer containing the resin composition can be removed without residue, and the in-plane uniformity can be removed. It is an object of the present invention to provide an etching method for a resin composition having a high alkalinity.

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

<1> A resin composition for etching a resin composition containing an alkali-insoluble resin and 50 to 80% by mass of an inorganic filler with an etching solution containing 15 to 45% by mass of an alkali metal hydroxide. An etching method for a resin composition, wherein the time from the end of the etching treatment step to the subsequent washing step with water is within 30 seconds.
<2> The etching method for the resin composition according to <1> above, wherein the etching solution contains 1 to 40% by mass of an ethanolamine compound.
<3> The etching solution contains at least one compound selected from the group consisting of 3 to 60% by mass of polyol compound, 2 to 20% by mass of polyvalent carboxylic acid, and 2 to 20% by mass of hydroxy acid. The etching method for the resin composition according to the above <1> or <2>, which comprises the above.

In the process of removing the resin composition containing the alkali-insoluble resin and the inorganic filler by the etching method for the resin composition of the present invention, the resin composition layer containing the resin composition can be removed without residue. It is possible to provide an etching method for a resin composition having high in-plane uniformity.

Schematic cross-sectional structural view of a solder resist pattern. Schematic cross-sectional structural view of a solder resist pattern. The cross-sectional process diagram which shows an example of the etching method of this invention.

Hereinafter, embodiments for carrying out the present invention will be described. The etching solution used in the etching method for the resin composition of the present invention (“etching method for resin composition” may be abbreviated as “etching method”) is an alkali-insoluble resin and 50 to 80% by mass. An etching solution for a resin composition containing an inorganic filler, which 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, the resin composition containing the alkali-insoluble resin can be removed by using the etching solution used in the present invention. 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 50 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 Is unlikely to occur, so the liquid has excellent stability over time. 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.

In the etching method of the present invention, in the process of removing the resin composition containing the alkali-insoluble resin and the inorganic filler using the above etching solution, the time from the end of the etching treatment step to the washing step of the next step is within 30 seconds. As a result, 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 that the dispersed state of the alkali-insoluble resin and the inorganic filler remaining in the etching-treated portion immediately after etching is related. Immediately after the etching process, the alkali-insoluble resin and the inorganic filler remaining in the etching process are in a dispersed state in which they are mixed with each other, and the resin composition layer is removed without residue by promptly washing with water in this dispersed state. can do. However, the time from the end of the etching process to the washing step exceeds 30 seconds, and the separation of the alkali-insoluble resin and the inorganic filler progresses, so that the components that are easily removed by washing with water and the components that are difficult to remove are separated. It is believed that a residue of the resin composition layer is generated after washing with water.

In the etching treatment step according to the present invention, methods such as immersion treatment, paddle treatment, spray treatment, brushing, and scraping can be used. Among these, the dipping treatment is suitable from the viewpoint of the uniformity of the etching treatment.

In the water washing step according to the present invention, a dip method, a paddle method, a spray method, brushing, scraping and the like can be used, and the spray method is most suitable from the viewpoint of cleaning efficiency and uniformity of the resin composition layer. The spray pressure is preferably 0.02 to 0.3 MPa.

The etching solution used in the present invention preferably 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, swells the resin composition, and makes it easy to uniformly dissolve the inorganic filler. 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. By containing the ethanolamine compound, the resin composition can be swollen, and the inorganic filler can be efficiently and uniformly dissolved by the alkali metal hydroxide.

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 (ie, 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 or 2- (ethylamino) ethanol which is a secondary amine; 2,2 which is a tertiary amine ′ -Methyliminodiethanol, N, N-dimethylaminoethanol and the like can be mentioned. Of these, 2- (methylamino) ethanol and 2- (2-aminoethylamino) ethanol are more preferable.

The etching solution used in the present invention contains at least one compound selected from the group consisting of 3 to 60% by mass of polyol compound, 2 to 20% by mass of polyvalent carboxylic acid, and 2 to 20% by mass of hydroxy acid. It is preferable to contain the above. When the etching solution contains a compound selected from the group consisting of a polyol compound, a polyvalent carboxylic acid, and a hydroxy acid, it becomes easy to disperse and remove the alkali-insoluble resin and the dissolved inorganic filler at the same time. Although the mechanism of this effect is beyond speculation, it is considered to be related to the above-mentioned dissolution / dispersion removal mechanism of the etching solution used in the present invention. In order to stably etch and remove the resin composition, 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. By containing a compound selected from the group consisting of polyol compounds, polyvalent carboxylic acids, and hydroxy acids, the etching solution has the function of collecting components that cannot maintain the film shape, and at the same time improves the performance of removing them. I believe. It is believed that the effect can stably remove the resin composition containing the alkali-insoluble resin and many inorganic fillers so that no residue remains.

The content of the polyol is preferably 3 to 60% by mass. When the content of the polyol is 3% by mass or more, the performance of dispersing them together is excellent, and when it is 60% by mass or less, the components are easily organized and sufficient removability can be obtained. The content of the polyol compound is more preferably 10 to 40% by mass.

The content of the polyvalent carboxylic acid is preferably 2 to 20% by mass. When the content of the polyvalent carboxylic acid is 2% by mass or more, the performance of dispersing the polyvalent carboxylic acid is excellent, and when it is 20% by mass or less, the components are easily organized and sufficient removability can be obtained. The content of the polyvalent carboxylic acid is more preferably 3 to 15% by mass.

The content of the hydroxy acid is preferably 2 to 20% by mass. When the content of the hydroxy acid is 2% by mass or more, the performance of dispersing all together is excellent, and when it is 20% by mass or less, the components are easily organized and sufficient removability can be obtained. The content of the hydroxy acid is more preferably 3 to 15% by mass.

As the polyol compound, any kind may be used, one kind may be used alone, or two or more kinds may be used in combination. Specific examples include glycerin, pentaerythritol, sorbitol, xylitol and the like. Of these, glycerin and sorbitol are more preferable.

The polyvalent carboxylic acid may be of any kind, may be used alone, or may be used in combination of two or more. Specific examples include oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), L-aspartic acid-N, N-2 acetic acid (ASAS). , Diethylenetriaminetetraacetic acid (DTPA) and salts thereof. Among these polyvalent carboxylic acids, malonic acid, maleic acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminetetraacetic acid (DTPA) and salts thereof are more preferable, and malonic acid and ethylenediaminetetraacetic acid (EDTA) and salts thereof are further preferable. Preferably, ethylenediaminetetraacetic acid (EDTA) and a salt thereof are particularly preferable.

As the hydroxy acid, any kind may be used, one kind may be used alone, or two or more kinds may be used in combination. Specific examples include glycolic acid, lactic acid, tartronic acid, glyceric acid, leucic acid, malic acid, tartaric acid, gluconic acid, citric acid, isocitrate, mevalonic acid, pantoic acid, hydroxyethyliminodiacetic acid, and hydroxyiminodi Succinic acid, quinic acid, salicylic acid, 4-hydroxyphthalic acid, 4-hydroxyisophthalic acid, cleosortic acid (homosalicylic acid, hydroxy (methyl) benzoic acid), vanillic acid, syring acid, hydroxypentanoic acid, hydroxyhexanoic acid, resorcil Examples thereof include acids, protocatechuic acid, gentidic acid, orseric acid, gallic acid, mandelic acid, atrolactic acid, melilothic acid, floretic acid, kumalic acid, umbiliic acid, coffee acid and the like, and salts thereof. Among these hydroxy acids, malic acid, tartaric acid, gallic acid, 4-hydroxyisophthalic acid and salts thereof are more preferable, tartaric acid and 4-hydroxyphthalic acid and their salts are more preferable, and tartaric acid and its salts are particularly preferable.

A coupling agent, a leveling agent, a colorant, a surfactant, an antifoaming 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.

In the present invention, the temperature of the etching solution is preferably 60 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 performing the process of removing the resin composition, etc., but the temperature of the etching solution is different. , More preferably 60 to 85 ° C, still more preferably 70 to 85 ° C.

The etching solution used in the present invention is an etching solution for a resin composition containing an alkali-insoluble resin and an inorganic filler. The content of the inorganic filler in the resin composition is 50 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 50% by mass, the etching does not proceed because the amount of the inorganic filler as the site dissolved by the etching solution is too small with respect to the entire resin composition. If 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 dissolves in an aqueous solution containing an alkali metal hydroxide. 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 alkali-insoluble resin in the present invention will be described. The alkali-insoluble resin is not particularly limited except that it is insoluble 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 to dissolve in an alkaline aqueous solution, and has an acid value (JIS K2501) that 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 alkali metal silicate, alkali metal hydroxide, alkali metal phosphate, alkali metal carbonate, ammonium phosphate, aqueous solution containing an inorganic alkaline compound such as ammonium carbonate, monoethanolamine, and the like. Organics such as diethanolamine, triethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, triethylamine, cyclohexylamine, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, trimethyl-2-hydroxyethylammonium hydroxide (choline) Examples thereof include an aqueous solution containing an alkaline compound.

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; novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac 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 include a phenol-based curing agent, a naphthol-based curing agent, an active ester-based curing agent, and a benzoxazine-based curing agent. 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, a tertiary amine compound and the like. 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 organometallic 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, and an organocobalt compound.

The resin composition containing the alkali-insoluble resin and the 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 used in the present invention, but the inorganic filler is partially or completely dissolved in the etching solution used in the present invention. Dispersion removal of the resin composition proceeds. When the resin is completely cured in the C stage, it becomes difficult for the etching solution used in the present invention to swell the resin composition layer and penetrate into the resin composition layer, making uniform etching difficult. become.

The thermosetting conditions from the A stage to the B stage are preferably 100 to 160 ° C. for 10 to 60 minutes, and more preferably 100 to 130 ° C. for 10 to 60 minutes, but are limited thereto. It's not a thing. When heated at a high temperature exceeding 160 ° C., thermosetting further progresses, and resin etching 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 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 to form the solder connection pad 3. 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 5 for etching the resin composition layer.

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

In the step (V), the metal mask 5 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.

Among the steps (I) to (V), the etching method of the present invention refers to the process from step (III) to the end of step (V) to the next step. That is, the water washing step of the present invention refers to a step of washing with water within 30 seconds after the step (V) is completed.

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 1-22, 25, 26)
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 to make the total amount 100% by mass, and methyl ethyl ketone and cyclohexanone were mixed 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 release layer, and a carrier foil were laminated in this order was prepared, and both were thermocompression bonded so that the copper foil and the resin composition layer were in contact with each other. After that, the release 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 width 400 mm x 500 mm, copper foil thickness 12 μm, base material thickness 0.1 mm) is patterned by etching to form a conductor pattern a. However, an epoxy resin glass cloth base material (circuit board 1) was obtained in which 10 pieces were uniformly arranged in the plane in the horizontal direction and 12 pieces in the vertical direction. 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 130 ° C. for 45 minutes to form a B-stage resin composition layer 4.

Subsequently, the copper foil 6 on the resin composition layer 4 is patterned by etching to form an opening in a predetermined region of the copper foil, and the resin with the metal mask 5 is used as the metal mask 5 for etching the resin composition layer. The composition layer 4 was prepared.

Next, an etching treatment step of immersing the resin composition layer 4 at 80 ° C. with the etching solutions shown in Tables 1 to 3 is carried out through the metal mask 5, and then tap water is performed 20 seconds later. A water washing step was carried out to remove the alkali-insoluble resin and the inorganic filler remaining in the etching-treated part by the spray treatment. Tables 1 and 2 show the composition of the etching solution and the time between the etching step and the washing step. Then, the surface was further washed by spraying with pure water.

Whether or not the resin composition layer 4 was reliably removed in the opening of the metal mask 5 was evaluated by "resin residue". In addition, "undercut" was evaluated as an evaluation of the deformation of the resin composition layer 4 in the opening shape. Further, as an evaluation of in-plane uniformity, the target opening diameter (target opening diameter) is the same, 120 openings b in the plane are observed, and the opening with the maximum opening diameter is opened. The aperture is set to the "maximum value", the opening diameter of the opening that minimizes the opening diameter is set to the "minimum value", and the fluctuation value (%) is calculated by "(maximum value-minimum value) / opening target value x 100", and the "surface "Internal uniformity" was evaluated. The results are shown in Tables 1 and 2. The criteria for each evaluation are shown below.

(Remaining resin)
◯: No resin composition remains on the surface.
○ △: A very small amount of resin composition remains on the surface, but this is not a problem.
Δ: A small amount of resin composition remains on the surface, but it can be easily removed by plasma cleaning treatment.
X: A level at which a large amount of resin composition remains on the surface after etching and is not removed by plasma cleaning treatment.

(undercut)
◯: No undercut is observed in the resin composition layer.
○ △: A very small undercut can be seen on the bottom surface of the resin composition layer.
Δ: A small undercut can be seen on the bottom surface of the resin composition layer, but this is not a problem.
X: A large undercut that poses a practical problem is seen on the bottom surface of the resin composition layer.

(In-plane uniformity)
◯: Very high uniformity. The fluctuation value is less than 3%.
○ △: High uniformity. The fluctuation value is 3% or more and less than 5%.
Δ: Uniform. The fluctuation value is 5% or more and less than 6%.
X: Not uniform. The fluctuation value is 6% or more.

(Example 23)
The etching treatment was carried out in the same manner as in Example 8 except that the content of the spherical fused silica was 55% by mass and the content of the biphenyl aralkyl type epoxy resin was 33% by mass. The results are shown in Table 2.

(Example 24: Comparative example)
The etching treatment was carried out in the same manner as in Example 8 except that the content of the spherical fused silica was 45% by mass and the content of the biphenyl aralkyl type epoxy resin was 43% by mass. Although the etching time was extended to 30 minutes, the resin composition layer could not be etched due to a large amount of resin residue on the surface of the conductor pattern and on the epoxy resin glass cloth base material. The results are shown in Table 2.

(Example 27-Example 36: Comparative example)
Etching by the same method as in Examples 1, 7, 8, 10, 12 and 13 except that the time between the etching step and the washing step is changed to 40 seconds during the dipping treatment for removing the resin composition layer 4. Processing was performed.

(Example 37: Comparative example)
The resin composition layer 4 with the metal mask 5 obtained by the same method as in Example 1 was etched by wet blasting, and then the metal mask 5 was removed. As a result of observing this with an optical microscope, there was a variation in the etching amount of the resin composition layer 4, and there was a place where the resin composition remained on the epoxy resin glass cloth base material. In addition, many scratches made by the blasting treatment were confirmed in the conductor pattern in which a part or all of the surface was exposed.

As can be seen from the results of Tables 1 to 3, in the present invention, the resin composition containing the alkali-insoluble resin and the inorganic filler has less occurrence of undercut and no residue of the resin composition as compared with the comparative example. It can be seen that it can be removed stably and that the in-plane uniformity is high.

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

1 Circuit board 1'Copper-clad laminate 2 Insulation layer 3 Solder connection pad, connection pad 3'Copper foil 4 Resin composition layer 5 Metal mask 6 Copper foil a Conductor pattern b Opening

Claims (3)

Etching for a resin composition by etching a resin composition containing an alkali-insoluble resin and an inorganic filler of 50 to 80% by mass with an etching solution containing an alkali metal hydroxide of 15 to 45% by mass. In the method, an etching method for a resin composition, characterized in that the time from the end of the etching treatment step to the subsequent washing step with water is within 30 seconds. The etching method for a resin composition according to claim 1, wherein the etching solution contains 1 to 40% by mass of an ethanolamine compound. The etching solution contains at least one compound selected from the group consisting of 3 to 60% by mass of polyol compound, 2 to 20% by mass of polyvalent carboxylic acid, and 2 to 20% by mass of hydroxy acid. The etching method for the resin composition according to claim 1 or 2.