JP3244835B2 - Manufacturing method of printed wiring board - Google Patents

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 circuit board using electrophotography, and more particularly, to a method for electrophotographic reversal development on a photoconductive layer provided on a wiring board by an electrodeposition method. The present invention relates to a method for manufacturing a novel printed wiring board provided with a toner image, and to a method for manufacturing a printed wiring board in which a toner layer is formed even inside a fine through hole prior to stripper processing.

[0002]

2. Description of the Related Art Conventionally, to manufacture a printed wiring board,
In general, after laminating a photosensitive film on a laminated board with copper foil on an insulating substrate, overlaying a photographic negative and exposing and developing, unnecessary copper foil other than the circuit pattern is removed by etching, and then A printed circuit was formed on an insulating substrate by removing the photosensitive film. In the method using this photosensitive film, since the thickness of the photosensitive film is generally as large as about 50 μm, the circuit pattern formed by exposure and development is not sharp, and it is possible to laminate the film uniformly on the copper foil surface. It was difficult, and in particular, it was almost impossible to cover the through-hole portion.

In order to improve the resolution and the like of a photosensitive film, Japanese Patent Application Laid-Open Nos.
No. 672 discloses a method for forming a photosensitive resist on a substrate by an electrodeposition method. In the formation of the photosensitive layer by the electrodeposition method, although the photosensitive layer can be uniformly thinned as compared with the lamination method, the sensitivity of the electrodeposition photoresist is generally low. Therefore, in the case of a so-called positive type in which a light irradiation part is solubilized in a processing liquid, energy of about several hundred mJ / cm ² is required to obtain sufficient solubility, and light irradiation is performed using a laser or the like. Was inappropriate. Also,
It was difficult to irradiate light inside the through-hole.

On the other hand, as a method of manufacturing a printed wiring board by a method other than a photosensitive resist, a method utilizing electrophotography is disclosed in West German Patent Nos. 1,117,391 and 2,52.
No. 6,720, No. 3,210,577;
No. 2437, No. 57-48736, No. 59-1684
62, etc., and JP-A-63-1296.
No. 89 proposes a method for producing a printed wiring board using an electrophotographic photosensitive member having sensitivity to a laser wavelength. In direct circuit drawing by a laser using this electrophotography, the required exposure amount is as low as 50 to 1 μJ / cm ^2, and therefore, the laser used can be a low-cost, low-output semiconductor laser or the like. For the photoconductive layer to be formed, a coating liquid in which a photoconductive compound is dispersed or dissolved in an organic solvent together with a suitable insulating resin is applied to a conductive substrate, or a coating once applied to a temporary substrate is applied by heat and pressure. The photoconductive layer could not be uniformly provided in the through-hole because it was transferred or provided on a conductive substrate.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a conductive substrate having a metal conductive layer provided on both sides of an electrically insulating substrate, a photoconductive layer provided on the metal conductive layer, and an electrophotographic method provided on the photoconductive layer. Forming a toner image, and then using a stripper to dissolve and remove the photoconductive layer other than the toner-attached portion, and, if necessary, in a method of manufacturing a printed wiring board in which the photoconductive layer-removed portion substrate surface is etched. An object of the present invention is to provide a method for manufacturing a printed wiring board which has excellent reproducibility of an exposed image, can perform uniform processing even in a through hole, and utilizes the high sensitivity characteristics of electrophotography. More specifically, it is an object of the present invention to provide a method for manufacturing a printed wiring board that can uniformly provide a photoconductive layer even in a through hole.

[0006]

Means for Solving the Problems The present inventors have studied to solve the above-mentioned problems, and as a result, have found that light is deposited on a conductive substrate metal conductive layer by providing a metal conductive layer on both surfaces of an electrically insulating substrate by an electrodeposition method. Providing a conductive layer, further forming a toner image on the photoconductive layer by electrophotography using reversal development, then dissolving and removing the photoconductive layer other than the toner image area, and optionally removing the photoconductive layer. In a method of manufacturing a printed wiring board for etching a substrate surface, it has been found that electrodes for reversal development may be provided on both sides of the substrate, and the present invention has been accomplished.

According to the present invention, a compound having photoconductivity and an electrodeposition resin are electrodeposited by an electrodeposition method using a metal conductive substrate for a printed wiring board as an electrode, and light is deposited on the conductive substrate and / or in a through hole. After forming a conductive layer, providing an electrode on both sides of the substrate via the toner liquid and facing the surface of the substrate, and performing reversal development, forming a toner image on the photoconductive layer by electrophotography, and then excluding the toner image portion The non-image portion photoconductive layer is dissolved and removed by a stripper, and if necessary, the non-image portion metal conductive layer is further subjected to etching treatment to produce a printed wiring board.

[0008] The electrodeposition method is a kind of coating method which has been performed for more than 20 years, and has already been put to practical use as a method for coating a body of an automobile or a photoresist for a part of a printed circuit board. The electrode has good characteristics of conforming to the surface, and has a feature that the film thickness can be made uniform irrespective of the surface shape of the substrate. Generally, the electrode is immersed in an aqueous dispersion of a resin having a cationic or anionic property. In this method, a current is applied to cause the ion species to migrate on the electrode surface to cause a chemical reaction on the electrode surface to lose ionicity, thereby insolubilizing the resin with water.

As the resin used for the electrodeposition of the present invention, a water-insoluble resin layer can be formed on the substrate by a usual electrodeposition method using a printed wiring board substrate as an electrode, and the electrophotographic properties including the chargeability are satisfied. However, it must have appropriate solubility with a stripper. In particular, if the substrate surface (copper layer) of the printed wiring board photoconductive layer-removed portion substrate is subjected to an acidic etching treatment, a resin having an anionic functional group is advantageously used in order to develop etching resistance. If the formed resin layer has a high composition ratio of anionic monomer, it is easily redissolved in water, the resin film becomes brittle, and the ionic conductivity is further increased, and the electrophotographic properties such as dark charging property are deteriorated. The resin composition of the electrodeposition resin according to the present invention is appropriately adjusted by copolymerizing an anionic monomer with a nonionic monomer.

[0010] Among resins having an anionic functional group, particularly, a monomer-containing copolymer having a carboxylic acid group and a phenol resin have a high charge retention ability and can be advantageously used. Examples of the monomer-containing copolymer having a carboxylic acid group include a copolymer of styrene and maleic acid monoester, and a copolymer of acrylic acid or methacrylic acid and their alkyl esters, aryl esters or aralkyl esters. Polymers are preferred. Further, a copolymer of vinyl acetate and crotonic acid is also good. Particularly preferred among phenol resins are phenol, o-cresol, m-cresol, and p-cresol.
A novolak resin obtained by condensing cresol with formaldehyde or acetaldehyde under acidic conditions can be mentioned.

Specific examples of the electrodeposition resin according to the present invention include styrene / maleic acid monoalkyl ester copolymer, methacrylic acid / methacrylic acid ester copolymer, styrene / methacrylic acid / methacrylic acid ester copolymer, acrylic Styrene and acrylic acid esters such as acid / methacrylic acid ester copolymer, styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate / crotonic acid copolymer, vinyl acetate / crotonic acid / methacrylic acid ester copolymer; Methacrylate, vinyl acetate,
Copolymers of vinyl benzoate and the like with carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid and fumaric acid, methacrylamide, phenolic hydroxyl group, sulfonic acid group, sulfone An amide group,
Examples thereof include a copolymer containing a monomer having a sulfonimide group and a phosphonic acid group, a phenol resin, and a xylene resin. These electrodeposition resins may be used alone or in combination of two or more.

For electrodeposition, it is necessary to uniformly disperse the above electrodeposition resin at least in the electrodeposition solution or more preferably to dissolve it. To that end, the anionic group in the resin is partially or organically or inorganicly base,
It is preferable to neutralize all of them. As the inorganic base, for example, sodium carbonate, sodium hydroxide, potassium hydroxide, ammonia and the like can be used. As the organic base, triethylamine, ethanolamine and the like can be used.

As the photoconductive material used for the photoconductive layer,
Organic and / or inorganic photoconductive materials can be used. Examples of the inorganic photoconductive material include cadmium sulfide, zinc oxide, and titanium oxide. Examples of the organic photoconductive material include metal-free or metal (oxide) phthalocyanine and naphthalocyanine, and derivatives thereof. Further, if necessary, a perinone compound, an oxadiazole compound, an anthranthrone compound, a sensitizing dye or the like may be used in combination.

The electrodeposition solution bath used for the electrodeposition of the present invention is basically composed of a water mixture of the above-mentioned photoconductive compound and resin. Solvents can also be used. Further, the resin component or the photoconductive compound may be in a state of being dispersed in water or an organic solvent or in a state of being partially dissolved. The amount of the photoconductive compound with respect to the resin varies depending on the resin composition, but is preferably in the range of about 0.1 to 40 parts by weight of the resin. Further, when the solid content concentration of the electrodeposition liquid bath is kept constant within the range of 1% by weight to 30% by weight, the film thickness can be easily controlled by the amount of electricity.

As the conductive substrate provided with a metal conductive layer on the electrically insulating substrate according to the present invention, "Printed Circuit Technology Handbook" (edited by Japan Printed Circuit Industry Association, published in 1987, published by Nikkan Kogyo Shimbun) And a general phenolic resin-impregnated laminate, an epoxy resin-impregnated laminate, or the like, as described in (1), and a copper foil bonded thereto.

If the photoconductive layer is thin, the charge required for toner development cannot be charged. Conversely, if the photoconductive layer is thick, not only the deterioration of the stripper is promoted, but also the thinning of the image is caused when the non-image portion photoconductive layer is removed. Since an image having good reproducibility cannot be obtained, the film thickness is set to 0.5.
It is important to set the electrodeposition conditions so as to adjust to 0 to 10 μm.

As the thickness of the copper foil, various thicknesses can be used. Generally, a thickness of 35 μm to 5 μm is used, but a thicker or thinner one can also be used. As the wiring density becomes higher and the line width of the conductor becomes thinner, it is better to use a thin copper foil.

In the electrodeposition, basically, a conductive substrate for printed wiring and a counter electrode made of a suitable metal are placed in a solution containing the above electrodeposited resin and a photoconductive compound, and the conductive substrate for printed wiring and the counter electrode are And by applying an appropriate potential between them.

As a toner for forming an image, a wet toner used for an electrophotographic printing plate can be used. However, in a later step, removal of a photoconductive layer in a non-image portion, and the exposed conductive material are performed. It must be resistant to etching of the layer and the like. In addition, it is necessary to use either positive or negative charging depending on the photoconductive compound to be used, the charging polarity at the time of corona charging, and the developing method.

The toner development is performed by bringing the above-mentioned charged photoconductor into contact with a toner dispersion liquid in the same manner as in the development of a general electrophotographic printing plate. And a reversal development method using a toner having the same polarity as the electrostatic latent image. In the case of a printed wiring board having a through hole, when the thickness of the substrate is larger than the hole diameter of the through hole, that is, when the so-called aspect ratio of the hole diameter and thickness is large, an electrostatic latent image is formed inside the through hole. It becomes difficult to form. In such a case, the potential of the electrostatic latent image formed in the through hole cannot be too high, and in the case of the normal development method using a toner having a charge of the opposite polarity to the electrostatic latent image, the It is difficult to form a uniform toner layer inside the hole, and it is necessary to adopt a so-called reversal development method using a toner having the same polarity as the electrostatic latent image.

As described above, a laser light source or the like can be used for exposing the formed photoconductive layer, but this depends on the type of the photoconductive compound used and the like. For example, when a フ タ -type phthalocyanine is used, a semiconductor laser can be used.
When an anthrone compound having a spectral absorption around m is used, an argon laser can be used.

A stripper is used as a method for dissolving and removing the toner-developed portion of the photoconductive layer where the toner image is not formed. Basically, a PS plate developing processor using an alkali developing solution is used. can do.

The etching is a step of removing the exposed copper foil by removing the photoconductive layer by the above-mentioned stripper. The above-mentioned "Printed Circuit Technology Handbook" (edited by the Japan Printed Circuit Industry Association, published in 1987, Nikkan Kogyo) An apparatus described in a newspaper company) can be used. Also,
The etchant may be any one that can dissolve and remove the copper foil, and a general etchant for printed circuit boards can be used.

Although a copper foil pattern necessary for a circuit can be basically obtained through the etching step, the photoconductive layer and the toner are present in the portions that have not been etched. These may be present as they are, but may not be necessary when connecting circuit components, chips, and the like. In this case, as in the case of manufacturing a printed wiring board using a general photosensitive polymer, these can be removed by treating with a solution having a higher alkalinity. Further, if necessary, an organic solvent such as methyl ethyl ketone or dioxane can be used.

In the electrodeposition step, the same apparatus as that used in the ordinary electrodeposition coating can be used. A base electrode to be electrodeposited on the electrodeposition layer and a counter electrode for passing electricity are provided, and a direct current is applied between the electrodes. By flowing, a photoconductive layer can be formed. The formed photoconductive layer is generally porous as it is,
The holes are filled by heat drying to form a uniform layer. In addition, through the drying step, a stable dark charging property can be obtained.

[0026]

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

Preparation of Electrodeposition Resin A mixture of 40 parts by weight of methyl methacrylate, 40 parts by weight of butyl acrylate, 20 parts by weight of acrylic acid and 2 parts by weight of azobisisobutyronitrile was kept at 100 ° C. in a nitrogen gas atmosphere. It was added dropwise to 90 parts by weight of dioxane over 3 hours, and an acrylic resin solution was obtained over 5 hours.

Fifty parts by weight of the resin solution for electrodeposition prepared at the electrodeposition destination were mixed with a χ-type metal-free phthalocyanine (Fastogen, manufactured by Dainippon Ink Co., Ltd.)
blue # 8120) After addition of 1 part by weight, triethylamine was added for neutralization, and deionized water was further added so that the solid content became 10% by weight to form an electrodeposition bath. Using this electrodeposition bath, a double-sided copper-clad laminate for printed wiring boards having a large number of through holes having a diameter of 0.6 mm and 1.2 mm (300 ×
300 × 1.6 mm, copper foil thickness: 18 μm) as an anode,
Electrodeposition was performed by applying a DC current of 120 V for 1 minute at a bath temperature of 25 ° C. The obtained film was washed with water and dried at 70 ° C. for 10 minutes to obtain a copper-clad laminate having a smooth photoconductive layer having a thickness of about 5 μm on both sides.

Evaluation of the Photoconductive Layer The formed photoconductive layer had good adhesion to the copper surface and was well covered even when the copper surface was uneven due to scratches or the like. When the cross section was examined separately, it was confirmed by a microscope and the like that the photoconductive layer was also formed uniformly on the inner wall of the through hole. The photoconductive properties of this copper-clad laminate were evaluated with an electrostatic field meter SP-428 manufactured by Kawaguchi Electric. When a corona applied voltage of +6.0 KV is applied, V
0 (initial potential) + 300 V, was DD ₁₀ (dark decay potential retention after 10 seconds) 91%.

Formation of a Toner Image A double-sided copper-clad laminate on which a photoconductive layer is formed is charged to +250 V in a dark place, and an electrostatic latent image having a line width of 40 μm is formed on the laminate by a laser plotter having a wavelength of 780 nm. Was formed on both sides. This latent image is obtained by grounding the copper of the double-sided copper-clad laminate 21 by using a developing device as shown in FIG. 1 and a developing device having reversal developing electrodes on both sides of the substrate as shown in FIG. And a developing bias of +120 V is applied to the two developing electrodes 13 and a positively chargeable liquid developer is supplied from the toner supply pipe 14, and the developer is reversely developed while being discharged from the toner discharge slit. . As a developer, a toner “ODP-TW” for Mitsubishi OPC printing system (manufactured by Mitsubishi Paper Mills, Inc.) was used.
After toner development, the substrate was placed in a hot air drier at 90 ° C. for 3 minutes to fix the toner image. When the occurrence of defects in the cross section and around the through hole was investigated separately, it was 0.6 m
It was confirmed that the toner was uniformly developed and fixed also in the through-hole portion and the peripheral portion of each of 50 through-holes having a diameter of m and 1.2 mm.

Removal of non-image area photoconductive layer Eluate "ODP-" for Mitsubishi OPC printing system
The toner image and the undissolved photoconductive layer under the toner image were formed as image portions by removing the photoconductive layer where no toner was attached using "DF _II ".

[0032] The wiring image made of a conductive toner and undissolved photoconductive layer formed on the substrate by etching an alkaline aqueous solution as an etching resist, the Baume 42 ° ferric chloride etching solution was heated to 35 ° C. in the substrate Spray pressure 2.5kg / c
The metal conductive layer not covered with the etching resist was etched by spraying with m ² for 1 minute. Thereafter, when the etching resist composed of the toner and the photoconductive layer was removed with methyl ethyl ketone, a copper circuit having a line width of about 40 μm was formed in the etching resist portions on both sides. Also,
Microscopic observation separately confirmed that the inner wall of 50 through-holes having a diameter of 0.6 mm and the inner wall of the through-hole of 1.2 mm and the copper layer on the periphery were also uniformly present.

[0033]

COMPARATIVE EXAMPLE A photoconductive layer was formed by an electrodeposition method in the same manner as in the example, charged to -250 V in a dark place, and exposed with a laser plotter as in the example. As shown in FIG. 3, a developing device in which a laminated plate on which an electrostatic latent image is formed is provided with a reversal developing electrode only on the upper portion of the substrate and an insulative plastic plate 24 having the same size as the reversal developing electrode is provided on the lower portion. , A toner for Mitsubishi OPC printing system "OD
Using a "P-TW" (manufactured by Mitsubishi Paper Mills), a bias voltage was applied in the same manner as in the example, and reversal development was performed to form toner images on both surfaces. After toner development, the substrate was placed in a hot air dryer at 90 ° C. for 3 minutes to fix the toner image. Separately,
The occurrence of defects in the through-hole portion and the peripheral portion of each of the 50 through-holes having a diameter of 0.6 mm and 1.2 mm was examined. As a result, the toner was uniformly developed and fixed in almost all the through-holes and the peripheral portion of the through-hole. However, with respect to the 1.2 mm through hole, it was confirmed that the toner at the lower portion of the through hole and the toner around the lower portion of the through hole became thin at five places. Further, the non-image area photosensitive layer was removed in the same manner as in the example, and etching treatment was performed. The portions corresponding to the above five portions were separately observed with a microscope. As a result, it was confirmed that the copper layer was partially removed.

[0034]

As described above, according to the method for producing a printed wiring board of the present invention, a copper-clad laminate having a through hole having a high aspect ratio can be subjected to electrophotography using a low-energy such as a semiconductor laser. An extremely high-resolution wiring circuit can be formed while using the exposure source, and the copper layer inside the through hole can be surely protected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a developing electrode used in the present invention. (A) is a front view, (B) is a bottom view, and (C) is a side view.

FIG. 2 is a side view of a developing device used in the present invention.

FIG. 3 is a side view of a developing device used as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Toner rectification chamber 12 Toner discharge slit 13 Developing electrode 14 Toner supply pipe 21 Double-sided copper-clad laminate on which an electrostatic latent image is formed 22 Entrance-side aperture roll 23 Exit-side aperture roll 24 Insulating substrate

Continuation of the front page (56) References JP-A-4-186991 (JP, A) JP-A-61-198795 (JP, A) JP-A-4-69990 (JP, A) JP-A-1-124879 (JP) JP-A-4-109255 (JP, A) JP-A-4-51253 (JP, A) JP-A-63-129689 (JP, A) JP-A-56-66863 (JP, A) 4-371969 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/06

Claims (1)

(57) [Claims] A photoconductive layer is provided by an electrodeposition method on an electroconductive substrate having a metal conductive layer provided on both sides of an electrically insulating substrate having a through hole, and a reverse development is performed on the photoconductive layer. A toner image is formed by an electrophotographic method used, and then a photoconductive layer other than a toner image portion is dissolved and removed, and in a method of manufacturing a printed wiring board in which a photoconductive layer removed portion substrate surface is etched, a method for reversal development is used. A method for manufacturing a printed circuit board, wherein electrodes are provided on both sides of the board.