JP6979336B2 - A method for manufacturing a printed wiring board, a printed wiring board and a photosensitive resin composition used in the manufacturing method. - Google Patents

Description

The present invention relates to a method for manufacturing a printed wiring board, a printed wiring board, and a photosensitive resin composition used in the method for manufacturing the printed wiring board.

In recent years, lightweight and compact products have been preferred for information and communication terminals that are convenient to carry, such as mobile devices, because of their intended use. Along with this, as the packaging method for semiconductor electronic components used inside the information and communication terminal, smaller and higher density CSPs (chip size packages) are often used. The technical requirements for printed wiring boards when mounting CSPs are also increasing.

Nickel / gold plating on the conductor on the surface of the printed wiring board is necessary for antioxidant and key contact points, and in addition, for high-density printed wiring boards such as mobile phones, lead wiring. Electrolytic nickel / gold plating treatment that does not require is effective. However, in high-density electronic components such as CSPs, especially where conduction is formed by solder connection, nickel / gold plating is not performed, that is, nickel / gold plating is performed only in partially required parts. It is desirable to perform processing.

For example, Patent Document 1 describes a step of forming a circuit wiring in a desired shape and partially applying a heat-curable or ultraviolet-curable plating resist to the surface layer portion of a printed wiring plate coated with a solder resist. A step of curing the plated resist by heating or irradiation with ultraviolet rays, a step of treating the conductor surface of the surface layer of the printed wiring board not coated with the plated resist with nickel / gold plating, and a step of peeling off the plated resist. The surface treatment method of the printed wiring board provided with the above is disclosed together with the effect that a high-quality partial nickel / gold-plated state can be formed in a short process, in a manufacturing time, and at a low cost.

Japanese Unexamined Patent Publication No. 2007-12735

However, the method for manufacturing a printed wiring board described in Patent Document 1 includes a step of partially applying a plating resist, so that the step is complicated.

Therefore, an object of the present invention is to provide a printed wiring board capable of forming a mountable pad portion that is not plated and a pad portion that has been plated by a simpler process that does not include a step of applying a plating resist. It is an object of the present invention to provide a manufacturing method and a photosensitive resin composition used for the manufacturing method of a printed wiring board.

As a result of diligent studies, the present inventors have formed a coating film of a photosensitive resin composition on a wiring board, provided an unreacted part, an incomplete reaction part, and a complete reaction part on the coating film, and developed the coating film. A resist film having openings for the 1-pad portion and the 2nd pad portion is provided, and after the plating treatment, the development residual film of the opening for the 2nd pad portion is removed to perform plating treatment with the plated 1st pad portion. We have found that it is possible to manufacture a printed wiring board having a second pad portion and a second pad portion, respectively, and have completed the present invention.

That is, the method for manufacturing a printed wiring board of the present invention includes a step of forming a coating film of a photosensitive resin composition on a wiring substrate having a conductor circuit, and an unreacted portion on the coating film of the photosensitive resin composition. A step of providing an incomplete reaction section and a complete reaction section, a step of forming a first pad section by development, and a step of forming an opening for a second pad section having a developing residual film, and a plating process on the first pad section. It is characterized by including a step of performing the above-mentioned plating treatment and a step of removing the development residual film to form the second pad portion.

In the method for manufacturing a printed wiring board of the present invention, it is preferable that the residual film ratio due to the development is 1% or more and less than 50%.

The printed wiring board of the present invention is obtained by the above-mentioned manufacturing method.

The photosensitive resin composition of the present invention is used in the method for manufacturing a printed wiring board.

According to the present invention, a plating process such as nickel / gold plating can be performed only on a partially required pad portion by a simpler step that does not include a step of applying a plating resist. That is, according to the present invention, there is provided a method for manufacturing a printed wiring board capable of forming a plated pad portion and a non-plated pad portion, respectively, and a photosensitive resin composition used for the manufacturing method. Can be done.

It is explanatory drawing of the process of this invention.

The method for manufacturing a printed wiring board of the present invention includes a step of forming a coating film of a photosensitive resin composition on a wiring substrate having a conductor circuit, and an unreacted portion and an incompleteness on the coating film of the photosensitive resin composition. A step of providing a reaction part and a complete reaction part, a step of forming a first pad part by development, a step of forming an opening for a second pad part having a development residual film, and a plating process on the first pad part. It is characterized by including a step and a step of removing the development residual film after the plating treatment to form the second pad portion.
In the past, a heat-curable or ultraviolet-curable plating resist was partially applied to the surface layer of a printed wiring board coated with a solder resist, but in the present invention, the coating film of the photosensitive resin composition is coated. An unreacted part, an incomplete reaction part and a complete reaction part are provided, and the developed residual film formed in the incomplete reaction part after development acts as a plating resist, and the developed residual film in the incomplete reaction part is removed after the plating treatment. To form a second pad portion that has not been plated. Therefore, a partially plated printed wiring board can be obtained in a simple process without using a plating resist.
In the method for manufacturing a printed wiring board of the present invention, the unreacted part, the incompletely reacted part, and the completely reacted part are also referred to as an unexposed part, a semi-exposed part, and an exposed part, respectively, and the plating process on the first pad part is performed. The first pad portion is also referred to as a plating forming pad portion.

The photosensitive resin composition of the present invention may be a negative type or a positive type, but is preferably a negative type. If it is a negative type, a developing residual film can be easily formed.
Regardless of whether the photosensitive resin composition is a negative type or a positive type, in the production method of the present invention, the photosensitive resin composition is applied on a wiring substrate and then activated by, for example, the shade of gray scale of the mask. The exposure amount of the energy ray is adjusted to form a contrast, and an unreacted part, an incomplete reaction part, and a complete reaction part are provided.
Here, when the photosensitive resin composition used in the production method of the present invention is a negative type, an unreacted portion removed by development and an incomplete reaction portion remaining as a development residual film by development and functioning as a substitute for a plating resist. And a complete reaction section that remains as a thicker film than the developed residual film and can function as a plating resist.
On the other hand, when the photosensitive resin composition used in the production method of the present invention is of the positive type, a complete reaction part removed by development and an incomplete reaction part remaining as a development residual film by development and functioning as a substitute for a plating resist. , An unreacted portion that remains as a thicker film than the developed residual film and functions as a plating resist is provided.
After the development, the first pad portion is subjected to a base treatment including at least plating, and after the plating treatment, the development residual film of the incomplete reaction portion is removed to form a second pad portion having a mountable surface.

That is, the present invention differs from the prior art described in Patent Document 1 in that the developed residual film formed in the opening of the coating film of the composition is used as a substitute for the plating resist. Therefore, the step of applying the plating resist becomes unnecessary, and the step becomes simple. By simplifying the process, it is possible to shorten the manufacturing time and reduce the manufacturing cost.

The advantage of the present invention is not limited to the simplification of the process. In the conventional plating resist, the electroless plating solution is attacked and eluted into the electroless plating solution to decompose the electroless plating solution, or the plated metal layer cannot be satisfactorily adhered to the surface of the external connection pad. Although there was a problem, in the present invention, such a plating resist is not formed, so that such a problem can be prevented from occurring.

Hereinafter, a method for manufacturing a printed wiring board according to the present invention will be described with reference to FIG. The method for producing a printed wiring board according to the present invention includes (1) a coating film forming step of a photosensitive resin composition, (2) a drying step, (3) an incomplete reaction portion forming step, (4) a developing step, and (5). It is preferable to include a heat curing step, a photocuring step, a plating treatment step, and a second pad portion forming step, but at least (1) a coating film forming step and (3) an incomplete reaction portion forming step. , (4) Development step, (6) Plating treatment step, and (7) Second pad portion forming step.

[(1) Coating film forming step of photosensitive resin composition]
In the present invention, a photosensitive resin composition that can function as a plating resist is used. The photosensitive resin composition may be a photosensitive resin composition soluble in an alkaline aqueous solution or a photosensitive resin composition soluble in an organic solvent, but may be a photosensitive resin composition soluble in an alkaline aqueous solution. preferable. When the photosensitive resin composition of the present invention is a negative type, it preferably contains an alkali-soluble resin and a photopolymerization initiator, and for example, a developed solder resist PSR-4000 series product manufactured by Taiyo Ink Mfg. Co., Ltd. is preferably used. be able to. On the other hand, when the photosensitive resin composition of the present invention is of the positive type, a composition containing an alkali-soluble resin and a photoacid generator such as diazonaphthoquinone can be used.

Hereinafter, a method for manufacturing a printed wiring board using the negative photosensitive resin composition of the present invention will be described with reference to FIGS. 1 (A) to 1 (E).
First, as shown in FIG. 1A, the photosensitive resin composition is applied onto the wiring board 1 having the conductor circuit 2 to form the coating film 3. As a method for applying the photosensitive resin composition, all known ink application methods such as screen printing method, spray coating method, roll coating method, dipping method, spin coating method and curtain coating method can be used. The material of the conductor circuit may be any conductive material such as copper, silver, and gold.

The film thickness of the coating film 3 is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. When it is 5 μm or more and 50 μm or less, the developed residual film 32A that can be easily removed by the forming step of the second pad portion can be easily formed in the incomplete reaction portion 32.
The coating film 3 of the photosensitive resin composition may be at least one that can function as a plating resist, but preferably one that can also function as a solder resist.

[(2) Drying step]
Subsequently, the coating film 3 is dried as needed. The coating film 3 of the photosensitive resin composition is dried by performing preliminary drying at a temperature in the range of, for example, 60 to 100 ° C. in order to volatilize the organic solvent in the photosensitive resin composition.

In forming the coating film 3 on the wiring board 1, a photosensitive resin composition is applied on an appropriate support in advance and then dried to form the coating film 3 (resin layer of a dry film). After overlaying the resin layer of the dry film on the wiring board 1, the resin layer of the dry film may be transferred onto the wiring board 1 by applying pressure to the dry film and the wiring board 1 (dry film method). In this case, the drying step may be omitted.

[(3) Incomplete reaction section forming step]
Subsequently, as shown in FIG. 1 (B), the coating film 3 is exposed to a pattern by irradiating the coating film 3 with active energy rays via the mask 4.

The active energy ray for exposure is selected so that the curing reaction of the photosensitive resin composition proceeds by being irradiated with the active energy ray. As the active energy ray for exposure, for example, ultraviolet rays, visible light, or near infrared rays are selected. When ultraviolet light is selected, the ultraviolet source is selected from, for example, chemical lamps, low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultrahigh pressure mercury lamps, xenon lamps and metal halide lamps.

The mask 4 includes three types of portions having different degrees of light transmission from each other. The mask 4 has, for example, a portion having light transmission (hereinafter referred to as a transmissive portion 41) and a portion having a light transmittance lower than that of the transmissive portion 41 (hereinafter referred to as a semi-transparent portion 42) due to shades of gray scale. It is provided with a portion having no light transmission (hereinafter referred to as a non-transmissive portion 43).

When the coating film 3 is pattern-exposed through the mask 4, the portion (exposed portion) corresponding to the transmissive portion 41 in the coating film 3 is irradiated with active energy rays, and a complete reaction portion 31 is provided. The portion (semi-exposed portion) corresponding to the semi-transparent portion 42 in the coating film 3 is irradiated with active energy rays at a lower exposure amount than the exposed portion, and an incomplete reaction portion 32 is provided. The portion (unexposed portion) corresponding to the impermeable portion 43 in the coating film 3 is not irradiated with the active energy ray, and the unreacted portion 33 is provided. That is, the complete reaction section 31 is a portion to which the active energy ray is irradiated at the time of exposure, and the incomplete reaction section 32 is a portion to which the active energy ray is irradiated with an exposure amount lower than that of the complete reaction section 31 when the active energy ray is irradiated. The unreacted portion 33 is a portion that is not irradiated with active energy rays during exposure. By designing the mask 4 so that the complete reaction section 31, the incomplete reaction section 32, and the unreacted section 33 are located at predetermined positions in the coating film 3, the amount of active energy rays irradiated to the photosensitive resin composition is applied. Can be adjusted.

When the coating film 3 is exposed in this way, the curing reaction of the photosensitive resin composition proceeds in the complete reaction section 31 of the coating film 3, and the photoreaction rate of the incomplete reaction section 32 is lower than that of the complete reaction section 31. , The curing reaction of the photosensitive resin composition proceeds. On the other hand, in the unreacted portion 33, the curing reaction of the photosensitive resin composition does not proceed.

In order to control the exposure amount in the complete reaction section 31, the incomplete reaction section 32 and the unreacted section 33 to a desired value, the mask 4 includes three types of portions having different degrees of light transmission as described above. It does not have to be. For example, the coating film 3 is first irradiated with active energy rays through a mask (first mask) that shields the unreacted portion 33 and does not shield the complete reaction portion 31 and the incomplete reaction portion 32, and then the first mask. A mask (second mask) that shields the incomplete reaction unit 32 and does not shield the complete reaction unit 31 is superimposed on one mask, and active energy rays are further transmitted through the first mask and the second mask. You may irradiate. Even in this case, the complete reaction section 31 is irradiated with the active energy ray, the incomplete reaction section 32 is irradiated with the active energy ray at a lower exposure amount than the complete reaction section 31, and the unreacted section 33 is activated. The energy rays will not be irradiated.

Further, in order to control the exposure amount in the complete reaction section 31, the incomplete reaction section 32 and the unreacted section 33 to a desired value, the mask 4 may not be used. For example, the exposure wavelength may be changed in each of the complete reaction unit 31, the incomplete reaction unit 32, and the unreacted unit 33. Further, direct imaging (DI) may be used in which the exposure amount of each of the complete reaction section 31, the incomplete reaction section 32 and the unreacted section 33 on the coating film 3 is adjusted by a program.

It is preferable to irradiate the active energy rays so that the photoreaction rate of the composition in the complete reaction section 31 is 50% or more, and more preferably 60% or more. When it is 50% or more, the coating film 3 which is not removed in the developing step and the second pad portion forming step can be satisfactorily formed in the complete reaction portion 31.

It is preferable to irradiate the active energy rays so that the photoreaction rate of the composition in the incomplete reaction section 32 is 1% or more and less than 50%, and more preferably 5% or more and 30% or less. When it is 1% or more and less than 50%, the developed residual film 32A that can be easily removed by the second pad forming step can be easily formed in the incomplete reaction section 32.
The residual film ratio is preferably 1% or more and less than 50%, and more preferably 5% or more and 30% or less. The residual film ratio (%) can be calculated by 100 × (thickness of the developed residual film / thickness of the coating film before development), and the thickness of the developed residual film is the entire surface of the second pad portion 52. It means the thickness in the state of covering.

[(4) Development process]
After providing the complete reaction section 31, the incomplete reaction section 32 and the unreacted section 33, the coating film 3 is developed with a developing solution. In the developing step, it is preferable to develop with an alkaline developer, but it may be developed with an organic solvent. The developed coating film 3 is shown in FIG. 1 (C). The unreacted portion 33 of the coating film 3 is removed from the wiring board 1 to form the first pad portion 51, while the complete reaction portion 31 and the incomplete reaction portion 32 of the coating film 3 remain on the wiring board 1. .. That is, the unreacted portion 33 is removed by development to form the first pad portion 51 for plating, while in the incomplete reaction portion 32, an opening having the developed residual film 32A is formed by development, and the developed residual film 32A is formed. Functions as a plating resist, and the complete reaction unit 31 remains as a thicker film than the developed residual film 32A during development and functions as a plating resist.

Specific examples of the alkaline developing solution include an aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, an aqueous solution of ammonium carbonate, an aqueous solution of sodium hydrogencarbonate, an aqueous solution of potassium hydrogencarbonate, an aqueous solution of ammonium hydrogencarbonate, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, and an aqueous solution of ammonium hydroxide. Examples thereof include an aqueous solution of tetramethylammonium hydroxide and an aqueous solution of lithium hydroxide. As the developing solution, organic amines such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine can also be used. The solvent in the alkaline developer may be water alone or a mixture of water and a hydrophilic organic solvent such as lower alcohols.

The film thickness of the incomplete reaction portion 32 after the developing step, that is, the developing residual film 32A is preferably 0.1 μm or more and 4 μm or less, and particularly preferably 0.2 μm or more and 2 μm or less. When it is 0.1 μm or more and 4 μm or less, it becomes easy to remove by the second pad portion forming step, and it also functions well as a plating resist.

[(5) Thermosetting and photo-curing steps]
The coating film 3 after the development treatment is subjected to either a thermosetting treatment or a photocuring treatment, if necessary. The thermosetting treatment and the photocuring treatment may be performed under conditions that can withstand the subsequent plating treatment.

After heating the complete reaction section 31 and the developed residual film 32A, the entire reaction section 31 and the developed residual film 32A may be irradiated with active energy rays. In this case, the curing reaction of the photosensitive resin composition that remains unreacted in the complete reaction section 31 and the developing residual film 32A proceeds. The thermosetting treatment may be performed after the photo-curing treatment, or each may be treated a plurality of times.

[(6) Plating process]
Next, as shown in FIG. 1 (D), the first pad portion 51 is subjected to a base treatment including at least plating 6 such as nickel / gold plating treatment. As the plating treatment here, in addition to the nickel / gold plating treatment, any of tin plating treatment, OSP treatment and the like can be used. Of these, for nickel / gold plating, either electroless nickel / gold plating or electrolytic nickel / gold plating can be used, but plating is performed on high-density wiring substrates used especially for mobile phones and smartphones. In this case, electroless nickel / gold plating is preferably used from the viewpoint of reliability.

The electroless nickel / gold plating treatment is performed under the following conditions, for example. First, degreasing, washing with water, pickling, soft etching, and washing with water are performed in this order mainly for the purpose of cleaning the wiring board 1 having the coating film 3. Next, after the catalyst is treated on the surface, it is put into a bathtub of a nickel plating solution at 90 ° C., and electroless nickel plating of about 5 μm is adhered at a plating rate of 3 to 5 minutes per 1 μm. Then, after washing with water, it is put into a bathtub of a gold plating solution at 90 ° C., and electroless gold plating of about 0.03 μm is adhered at a plating rate of 3 to 5 minutes.

Since the plating process is performed at a plating temperature of 90 ° C., in the conventional technique, the plating resist elutes, causing problems such as contaminating the plating solution. In addition, the contaminated plating solution surface-treats the wiring substrate. The quality of the nickel / gold plating is poor, and it is difficult to obtain a good printed wiring board. In contrast, in the present invention, since a plating resist is not used, the plating solution is not contaminated.

[(7) Second pad forming step]
Next, as shown in FIG. 1 (E), the developing residual film 32A is removed to form the second pad portion 52. As shown in FIG. 1 (E), after the processing for removing the developing residual film 32A, the second pad portion 52 having a mountable surface is formed. The treatment for removing the developing residual film 32A includes a chemical treatment using an acid, an alkali, a solvent, etc., and a physical treatment using a laser, plasma, etc. be.

Further, it is desirable to further perform a water-soluble preflux treatment or a solder surface treatment such as a solder leveler on the second pad portion 52 on which the mountable surface is formed in order to protect the surface of the component mounting pad from oxidation.
In FIG. 1, the width of the opening for the first pad portion and the opening for the second pad portion is narrower than the width of the conductor circuit, but may be wider.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

The solder resist PSR-4000 EG30 for developing spray coating manufactured by Taiyo Ink Mfg. Co., Ltd. was applied to the entire surface by screen printing on a patterned copper foil substrate (wiring substrate) and dried at 80 ° C. for 20 minutes. The film thickness of this dry coating film was 20 μm. Next, a photomask having a light transmittance of 50% to the incomplete reaction part and a light transmittance of 100% to the complete reaction part was applied to this substrate, and ultraviolet rays were patterned and exposed at ^{an exposure amount of 600 mJ / cm 2.} .. The photoreaction rate of the composition in the complete reaction section was 70%, and the photoreaction rate of the composition in the incomplete reaction section was 30%. An FT-IR manufactured by PerkinElmer Co., Ltd. was used for measuring the photoreaction rate.
Then, it was developed with a 1 mass% sodium carbonate aqueous solution having a spray pressure of 1.5 kg / cm ² to form a resist pattern in which a first pad portion and an opening for a second pad portion having a development residual film were formed. Here, the developed residual film was 1 μm, and the residual film ratio was 5%. Then, the substrate was heated in a closed oven under the thermosetting condition of 150 ° C. × 60 minutes.

The test substrate prepared as described above is immersed in an acidic degreasing solution at 30 ° C. (20% by volume aqueous solution of Metex L-5B manufactured by MacDermid Co., Ltd.) for 3 minutes to degreas, and then in running water for 3 minutes. Soaked and washed with water. Next, the test substrate was immersed in a 14.3 mass% aqueous solution of ammonium persulfate at room temperature for 3 minutes, soft-etched, and then immersed in running water for 3 minutes and washed with water. The test substrate was immersed in a 10% by volume sulfuric acid aqueous solution at room temperature for 1 minute, then immersed in running water for 30 seconds to 1 minute and washed with water. Next, the test substrate was immersed in a catalyst solution at 30 ° C. (a 10% by volume aqueous solution of a metal plate activator 350 manufactured by Meltex Inc.) for 7 minutes, the catalyst was applied, and then the test substrate was immersed in running water for 3 minutes. Washed with water. The test substrate to which the catalyst was applied was immersed in a nickel plating solution at 85 ° C. (Meltex Co., Ltd., 20% by volume aqueous solution of Melplate Ni-865M, pH 4.6) for 20 minutes to perform electroless nickel plating. gone. The test substrate was immersed in a 10% by volume sulfuric acid aqueous solution at room temperature for 1 minute, then immersed in running water for 30 seconds to 1 minute and washed with water. Next, the test substrate was immersed in a gold plating solution at 95 ° C. (manufactured by Meltex Co., Ltd., an aqueous solution of Auroralless UP 15% by volume and potassium gold cyanide 3% by volume, pH 6) for 10 minutes for electroless gold plating. After that, it was immersed in running water for 3 minutes and washed with water, and then immersed in warm water at 60 ° C. for 3 minutes and washed with hot water. After being thoroughly washed with water, the water was thoroughly drained and dried to obtain an electroless gold-plated test substrate on the copper pad portion at the position corresponding to the opening.
After that, the developing residual film is removed with a stripping solution of an aqueous sodium hydroxide solution (3% by mass, liquid temperature 50 ° C.), and the copper pad portion is plated and has a mountable copper pad portion and is not plated. Obtained a printed wiring board.

As described above, according to the method for manufacturing a printed wiring board of the present invention, a copper pad portion that has been subjected to a base treatment including gold plating and a base including gold plating by a simpler process without using a plating resist. It can be seen that a printed wiring board having an untreated copper pad portion can be manufactured.

1 Wiring board 2 Conductor circuit 3 Coating film 31 Complete reaction part 32 Incomplete reaction part 32A Unreacted film 33 Unreacted part 4 Mask 41 Transparency part 42 Semi-transparent part 43 Non-transparent part 51 First pad part 52 Second Pad part 6 plating

Claims (2)

A process of forming a coating film of a photosensitive resin composition on a wiring board having a conductor circuit, and
A step of providing an unreacted portion, an incompletely reacted portion, and a completely reacted portion on the coating film of the photosensitive resin composition.
A step of forming a first pad portion by development and forming an opening for a second pad portion having a development residual film, and
The process of plating the first pad portion and
After the plating treatment, the step of removing the development residual film to form the second pad portion and the step of forming the second pad portion.
A method for manufacturing a printed wiring board, which comprises. The method for manufacturing a printed wiring board according to claim 1, wherein the residual film ratio after development is 1% or more and less than 50%.

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