JP2002246726A - Method for producing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a printed wiring board, in which conductors having a high etch factor can be obtained in fine circuit pattern using a subtractive method. SOLUTION: A printed wiring board is produced by forming a non-curable alkaline soluble polymer layer on a conductive substrate obtained, by forming a metal conductive layer on an electrically insulating substrate, forming a photoresist layer of 0.5-5 μm thick thereon, forming a two layer resist pattern by performing exposure of a circuit pattern and alkaline development, and then removing the metal conductive layer by etching, other than the resist pattern part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly, to a method for manufacturing a printed wiring board for forming a fine and highly accurate circuit pattern by a subtractive method.

[0002]

2. Description of the Related Art A method for manufacturing a printed wiring board is roughly classified into a subtractive method and an additive method. The subtractive method is a method in which an etching resist layer is formed on a conductive substrate in which a metal conductive layer such as copper is provided on an electrically insulating substrate, and the metal conductive layer not covered with the etching resist layer is removed by etching. The additive method is a method of forming a metal conductive layer only on a wiring pattern portion on an electrically insulating substrate. Other than these, a wiring transfer method, a semi-additive method, and the like have been proposed. Among them, the subtractive method has advantages such as strong bonding strength between a circuit and an insulating plate, high reliability and low cost, and the ability to form an electroplated copper through-hole. . As a method of providing an etching resist layer by a subtractive method, a method using a photosensitive layer of a photosensitive material such as a dry film and a liquid photoresist is generally used.

[0003] With the recent trend toward miniaturization and multi-functionality of electronic devices, the density of printed wiring boards used inside the devices and the miniaturization of circuit patterns are being promoted. Conductor width is 90 to 130 μm,
Printed wiring boards having a fine pattern with a conductor gap of 150 to 180 μm have been manufactured. Further, as the density and the wiring are further increased, a circuit having a conductor width and a conductor gap of 70 μm or less is required. As a result, requirements for pattern accuracy and impedance are also increasing.

At present, the most mainstream subtractive method is:
When forming a fine pattern such as a conductor width or a conductor gap of 70 μm or less, it is of course necessary to raise the technical level and management level of the entire production line. Among them, the exposure step and the etching step are the major points. Certainly. For example, in the case of exposure, the light parallelism of the exposure apparatus and the adhesion between the film and the substrate become important. In the case of etching, liquid composition management, liquid spray angle and strength on the substrate, and the like are important.

However, in the case of processing using a dry film resist, since the resist film has a high film thickness of 15 to 75 μm and further has a cover film such as a polyester film, the light parallelism and the substrate adhesiveness are poor. Even if the improvement is attempted, the light scattering at the time of exposure is limited, so that it is very difficult to produce a fine pattern of 70 μm or less at the time of the resist pattern. In the case of a liquid photopolymer, it is more advantageous for a fine pattern than a dry film. However, since a film thickness of 10 μm or more is required, there is also a problem of light scattering, and a fine pattern of 50 μm or less is produced. Is difficult.

One of the features of the subtractive method is side etching which proceeds from the side of the conductor in etching. In the case of a dry film or liquid photoresist, since the circuit portion is hardened, the resist portion has no flexibility, the etching solution easily enters the lower side of the overhang portion, the side etching easily proceeds, and the etch factor increases. Even if the optimal etching conditions such as the liquid composition management and the liquid spray angle and strength on the substrate are adjusted to suppress the amount of side etching, the etch factor greatly changes in the range of 2 to 10, and the etch factor is in the range of 2 to 10. However, there is a problem that the number of conductor wires having a low value is increased. In order to secure a stable impedance and a highly accurate pattern, it is necessary to improve the etch factor without variation.

As described above, in the current subtractive method, there is a limit in forming a fine and high-etch-factor conductor circuit, and a semi-additive method has been proposed and put into practical use as a means for satisfying them. is there. The semi-additive method proceeds through steps of catalyzing treatment, thinning by electroless copper plating, pattern formation, patterned copper plating, resist metal plating, plating resist peeling, and etching. For the semi-additive method, the normal 18
5-10μm, much thinner than copper foil thickness of μm or 35μm
Starting from a copper-clad laminate of copper foil, the etching depth required for forming a conductor pattern can be significantly reduced, which is very suitable for etching a fine pattern. However, as described above, there are a problem that the number of steps is large, which is troublesome and expensive, and a problem that it is difficult to form a fine resist circuit.

[0008]

The present invention also relates to a method for manufacturing a printed wiring board by a subtractive method.
An object of the present invention is to provide a method for manufacturing a printed wiring board capable of obtaining a conductor having a fine circuit pattern and a high etch factor.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that a non-curable alkali-soluble polymer layer is formed on a conductive substrate having a metal conductive layer provided on an electrically insulating substrate. Is formed, a photoresist layer is formed thereon, the circuit pattern is exposed, and alkali development is performed.
It has been found that a printed wiring board having a fine conductor having a high etch factor can be manufactured by forming a two-layer resist pattern and etching away the metal conductive layer other than the resist pattern portion.

Further, the thickness of the above-mentioned photoresist layer is 0.1 mm.
By forming the wiring in the range of 5 to 5 μm, a printed wiring board having a finer conductor having a higher etch factor could be manufactured.

That is, by making the photoresist layer much thinner than the conventional film thickness of 10 μm or more, the influence of light scattering is reduced, which is advantageous for fine pattern exposure. Further, since the lower layer was present, even if the photoresist layer was thinned, it functioned as an etching resist. In addition, since the lower layer of the two-layer resist does not have photocurability, the overhanged portion sags as the etching proceeds. Therefore, the flow of the metal etchant in the lateral direction is hindered, and the influence of the side etching of the conductor can be reduced. Also, as the photoresist layer becomes thinner,
Increased sensitivity and quicker resist stripping were secondarily made possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a printed wiring board according to the present invention will be described in detail.

A typical example of a conductive substrate provided with a metal conductive layer on the electrically insulating substrate according to the present invention is a substrate in which a copper foil or the like is bonded as a metal conductive layer to a paper base phenol resin or a glass base epoxy resin. It is typical. Examples of these laminates are described in "Printed Circuit Technology Handbook" (edited by The Japan Printed Circuit Industries Association, 1987, published by Nikkan Kogyo Shimbun), and any desired laminates can be used.

The thickness of the electrically insulating substrate is from 60 μm to 3.
It is about 2 mm, and its material and thickness are selected according to the final use form as a printed wiring board. For a thin substrate, a plurality of thin substrates may be laminated.

Various thicknesses of the metal conductive layer can be used. In general, those having a thickness of 12 to 35 μm are used, but thicker and thinner ones can also be used. . As the wiring density increases and the line width of the circuit decreases, it is preferable to use a thinner metal conductive layer. In some cases, the surface is subjected to half-etching treatment in order to produce a product having a thickness of several μm.

The metal used for the metal conductive layer is copper,
Silver, aluminum, stainless steel, nichrome, tungsten and the like.

The non-curable alkali-soluble polymer layer according to the present invention comprises at least a non-curable alkali-soluble polymer, and includes a carboxylic acid group, methacrylic acid, methacrylamide, phenolic hydroxyl group, sulfonic acid group, and sulfonamide group. , A sulfonimide group, a copolymer containing a monomer having a phosphonic acid group, and a phenol resin,
Xylene resin and the like can be mentioned. Specific examples include styrene / maleic acid monoalkyl ester copolymer, methacrylic acid / methacrylic acid ester copolymer, styrene / methacrylic acid / methacrylic acid ester copolymer, acrylic acid / methacrylic acid ester copolymer, and methacrylic acid. / Methacrylic acid ester / acrylic acid ester copolymer, styrene / methacrylic acid / acrylic acid ester copolymer,
Styrene such as styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate / crotonic acid copolymer, vinyl acetate / crotonic acid / methacrylic acid ester copolymer, vinyl benzoate / acrylic acid / methacrylic acid ester copolymer And copolymers of the above carboxylic acid-containing monomers with acrylic acid esters, methacrylic acid esters, vinyl acetate, vinyl benzoate and the like. These alkali-soluble polymers may be used alone or in combination of two or more.

"Non-cured" means that it is not cured by ultraviolet rays, heat, or the like. Curing, for example, by ultraviolet light,
Certain groups undergo a chemical reaction between the molecules of the linear polymer,
This can be explained by a net-like connection.

If the thickness of the non-curable alkali-soluble polymer layer according to the present invention is too large, side etching in the alkali developing step becomes excessive, line thinning tends to occur, and deterioration of the alkali developing solution is promoted. If the thickness is too small, there is a reduction in etching resistance, which is essential as an etching resist, and a reduction in adhesion to a metal conductive layer. Therefore, the thickness of the alkali-soluble polymer layer is 0.5 to 20.
μm is preferable, and among them, 2 to 10 μm is particularly preferable.

The non-curable alkali-soluble polymer layer according to the present invention is formed by applying an alkali-soluble polymer dissolved in a solvent on a conductive substrate and removing the solvent by heating to form a desired thickness. I do. The coating method can be performed by a dip coating method, a bar coating method, a spray coating method, a roll coating method, a spinner coating method, a screen printing method, an electrodeposition method, or the like, but is not particularly limited as long as a desired film thickness can be formed. Further, two-layer simultaneous coating with a photoresist layer can also be applied.

The solvent used for the non-curable alkali-soluble polymer according to the present invention may be any solvent which can be uniformly dissolved, and specifically, methanol, ethanol, 1-propanol, 1-methoxy-2- Alcohols such as propanol, THF, 1,4-dioxane,
Ethers such as 1,2-dimethoxyethane and ethylene glycol monomethyl ether; ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene; ethyl acetate, methyl acetate, isobutyl acetate and the like And amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, etc., but are not limited thereto, and application methods and drying conditions, etc. Can be selected and used. Regarding the solid content concentration of the coating liquid, an appropriate concentration can be selected depending on the coating method, drying conditions, and the like.

As the resist material used for the photoresist layer according to the present invention, a generally used liquid resist for forming a circuit or a resist for electrodeposition coating can be used. Can be used. These resist materials can be found in various ways, such as a photosensitive area, a sensitivity, a difference between a negative type and a positive type depending on an exposure method, a need for post-exposure and post-hardening treatment, and the like. Even if there is, it is applicable.

If the thickness of the photoresist layer according to the present invention is too large, light scattering at the time of exposure occurs.
Film formability and etching resistance are reduced. Therefore, the thickness of the photoresist layer is preferably from 0.1 to 10 μm, and particularly preferably from 0.5 to 5 μm.

Further, the relationship between the thickness of the alkali-soluble polymer layer and the thickness of the photoresist layer according to the present invention is that the overhang portion of the resist is apt to hang down and the etch factor is increased. Is preferably thicker than the photoresist layer.

The photoresist layer according to the present invention is formed by forming a lower non-curable alkali-soluble polymer layer, coating the resist composition again, and removing the solvent by heating to obtain a desired film thickness. Is particularly easy to form. Again, the application method is not particularly limited, but examples include dip coating, bar coating, spray coating, roll coating, spinner coating,
A screen printing method, an electrodeposition method and the like can be mentioned. Further, two-layer simultaneous coating with a non-curable alkali-soluble polymer layer can also be applied. Lamination is performed when a dry film is applied to the photoresist layer.

The circuit pattern exposure method according to the present invention includes reflection image exposure using a xenon lamp, high-pressure mercury lamp, low-pressure mercury lamp, ultra-high-pressure mercury lamp, UV fluorescent lamp as a light source, single-sided and double-sided contact exposure using a film mask, and the like. And scanning exposure with UV laser light. When performing scanning exposure, 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, and an excimer laser is used according to the emission wavelength. Exposure can be performed by wavelength-converted scanning exposure, or by scanning exposure using a liquid crystal shutter or a micromirror array shutter.

In the alkali development according to the present invention, an unreacted portion of the photoresist layer which has not been cured is removed using an alkaline aqueous solution as a developing solution, and the underlying alkali-soluble polymer is removed at the same time. A pattern is formed. The developer contains a basic compound,
For example, alkali metal silicate, alkali metal hydroxide,
Inorganic basic compounds such as phosphoric acid and alkali metal carbonate, phosphoric acid and ammonium carbonate, and organic basic compounds such as ethanolamines, ethylenediamine, propanediamine, triethylenetetramine, and morpholine can be used. The above basic compounds can be used alone or as a mixture. Generally, a weak alkaline aqueous solution such as an aqueous sodium carbonate solution is used. Similarly, in the present invention, a developing solution suitable for the photoresist and the alkali-soluble polymer to be used is used.

In the method for manufacturing a printed wiring board of the present invention,
The exposed metal conductive layer other than the circuit pattern portion of the resist is removed by etching. In the etching step, a method described in “Printed Circuit Technology Handbook” (edited by the Japan Printed Circuit Industry Association, published in 1987, published by Nikkan Kogyo Shimbun) or the like can be used. The etching solution may be any solution that can dissolve and remove the metal conductive layer and at least the alkali-soluble polymer layer has resistance. In general, when a copper layer is used as the metal conductive layer, an aqueous ferric chloride solution, an aqueous cupric chloride solution, or the like can be used.

After the etching step, the resist pattern can be removed by treating the resist pattern with a solution having a higher alkalinity than the developer used in the alkali development.
Generally, an aqueous solution of sodium hydroxide or the like is used. Similarly, in the present invention, a solution suitable for the photoresist to be used and the non-curable alkali-soluble polymer is used. If necessary, methyl ethyl ketone, dioxane, methanol, ethanol, propanol and the like can also be used.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

Example 1 Double-sided copper-clad laminate (area 340 mm × 510 mm, copper foil thickness 12 μm, substrate thickness 0.1 mm, manufactured by Mitsubishi Gas Chemical, CC
Using L-E170), a coating solution having the composition shown in Table 1 was applied by dip coating, and dried by heating at 120 ° C. for 15 minutes to form a non-curable alkali-soluble polymer layer on a copper-clad laminate by about 5 μm.
The thickness was set to μm.

[0032]

[Table 1]

Next, a negative type liquid photoresist (manufactured by Taiyo Ink Mfg. Co., Ltd., "PER-20") is applied using a roll coater and dried to form a film on the non-curable alkali-soluble polymer layer. A photoresist layer having a thickness of about 2 μm was provided.

The substrate on which the two-layer film was formed was exposed with a UV exposure device having high parallel light using a mask film having a circuit pattern having a conductor width and a conductor gap of 30 μm. Next, by performing alkali development with a 1% by weight aqueous solution of sodium carbonate (solution temperature: 35 ° C.), the photoresist layer other than the exposed portion and the non-curable alkali-soluble polymer layer below it are removed, and 3
A resist pattern consisting of two layers, in which a circuit portion having a conductor width of 0 μm and a gap was reproduced without being crushed, was formed.

Further, the substrate on which the resist pattern was formed was treated with a ferric chloride solution (40 ° C., spray pressure: 3.0 kg /
cm ² ) to remove the copper layer in portions not covered with the resist pattern. Next, the substrate was treated with a 3.0% by weight sodium hydroxide solution at 40 ° C. to remove the remaining resist layer, thereby obtaining a printed wiring board. When the obtained printed wiring board was observed with a microscope, 30 μm was observed on the photomask.
The portion having the conductor width and gap of 8 μm was narrowed by 8 μm by side etching or the like, and was formed as a metal pattern having a conductor width of 22 μm and a conductor gap of 38 μm.

Example 2 Double-sided copper-clad laminate (area 340 mm × 510 mm, copper foil thickness 12 μm, substrate thickness 0.1 mm, Mitsubishi Gas Chemical, CC
Using LE-E170), a coating solution having the composition shown in Table 1 was applied by dip coating, and dried by heating at 120 ° C. for 15 minutes to form a non-curable alkali-soluble polymer layer on a copper-clad laminate by about 3 μm.
Several sheets having a thickness of 10 to 10 μm were produced.

Next, a negative type liquid photoresist (manufactured by Taiyo Ink Mfg. Co., Ltd., "PER-20") is applied using a roll coater and dried to form a film on the non-curable alkali-soluble polymer layer. About 0.1, 0.5, 3.0, 5,.
Photoresist layers having five different thicknesses of 0, 8, and 0 μm were provided so as to be thinner than the thickness of the non-curable alkali-soluble polymer layer.

The substrate on which the two-layer film was formed was exposed using a mask exposure film having a circuit pattern having a conductor width and a conductor gap of 20 to 130 μm by a UV exposing machine having high parallel light. Subsequently, the photoresist layer was treated with a 1% by weight aqueous solution of sodium carbonate (solution temperature: 35 ° C.) until the photoresist layer other than the exposed portion and the non-curable alkali-soluble polymer layer thereunder were removed, and the alkaline development was completed.

Further, the substrate on which the resist pattern was formed was treated with a ferric chloride solution (40 ° C., spray pressure: 3.0 kg /
cm ² ) to remove the copper layer in portions not covered with the resist pattern. Next, the substrate was treated with a 3.0% by weight sodium hydroxide solution at 40 ° C. to remove the remaining resist layer, thereby obtaining a printed wiring board. Observation of the obtained printed wiring board with a microscope to confirm the reproducibility of the conductor width and the conductor gap resulted in the results shown in Table 2. In addition, for each of the fabricated products, the cross-section of the conductor circuit was observed and the value of the etch factor was measured.

[0040]

[Table 2]

As shown in Table 2, when the thickness of the photoresist layer was in the range of 0.5 to 5.0 μm, a circuit having a conductor width and a conductor gap of 70 μm or less was successfully produced. With respect to the photoresist layer having a thickness of 8.0 μm, a fine pattern of 70 μm or less was not obtained, but good etching characteristics were obtained, and a good circuit having a large etch factor was obtained at 100 μm or more. . Even when the photoresist layer thickness is smaller than 0.5 μm,
Although a fine pattern was not obtained, a conductor having a very large etch factor could be produced.

Comparative Example 1 Double-sided copper-clad laminate (area 340 mm × 510 mm, copper foil thickness 12 μm, substrate thickness 0.1 mm, manufactured by Mitsubishi Gas Chemical, CC
LE-170), and without providing a non-curable alkali-soluble polymer layer as a lower layer, a negative-type liquid photoresist (“PER-20” manufactured by Taiyo Ink Mfg. Co., Ltd.)
Is applied using a roll coater and dried, and about 5, 1
A photoresist layer having a thickness of 0 μm was provided.

Further, the conductor width and the conductor gap are 20 to 13
Using a mask film having a circuit pattern of 0 μm, exposure was performed with a UV exposure machine having high parallel light. Then, a 1% by weight aqueous solution of sodium carbonate (liquid temperature 3
(5 ° C.) until the photoresist layer other than the exposed portions was removed, and the alkaline development was terminated.

Further, the substrate on which the resist pattern was formed was treated with a ferric chloride solution (40 ° C., spray pressure: 3.0 kg /
cm ² ) to remove the copper layer in portions not covered with the resist pattern. Next, the substrate was treated with a 3.0% by weight sodium hydroxide solution at 40 ° C. to remove the remaining resist layer, thereby obtaining a printed wiring board.

Those formed with a film thickness of about 5 μm are
Mulling, defects in pinholes, peeling of the copper foil and the resist layer, etc. occurred frequently, and it was found that they did not function as an etching resist. With respect to the film formed with a film thickness of 10 μm, alkali development and etching were successfully completed, and a circuit was formed. Therefore, the circuit was observed with a microscope to confirm the reproducibility of the conductor width and the conductor gap. As a result, the conductor of 80 μm or less has collapsed or jumped lines,
The following circuits could not be successfully manufactured.

The cross-section of the conductor circuit obtained with a resist film thickness of 10 μm was observed, and the values of the etch factors were measured. The results were 1 to 9. The variation in the values of the etch factors was large. It is 3 when determined, compared to the value of the etch factor described in Table 2 when two layers of resist are used.
It is an extremely small value.

[0047]

As described above, in the method for manufacturing a printed wiring board of the present invention, a non-curable alkali-soluble polymer layer is formed on a conductive substrate, even if the subtractive method is used. A photoresist layer having a thickness in the range of 0.5 to 5 μm is formed, a circuit pattern is exposed, alkali development is performed, a two-layer resist pattern is formed, and a metal conductive layer other than the resist pattern portion is removed by etching. This has an excellent effect that a printed circuit board having a conductor having a fine circuit pattern and a high etch factor can be manufactured.

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Claims (2)

[Claims] 1. A non-curable alkali-soluble polymer layer is formed on a conductive substrate provided with a metal conductive layer on an electrically insulating substrate, a photoresist layer is formed thereon, and a circuit pattern is exposed. A method for manufacturing a printed wiring board, comprising: performing alkali development to form a two-layer resist pattern, and etching away a metal conductive layer other than the resist pattern portion. 2. The method according to claim 1, wherein the photoresist layer has a thickness of 0.5 to 0.5.
The method for producing a printed wiring board according to claim 1, wherein the thickness is in a range of 5 µm.